Ornamental Notes by waqasalisahil




Department of Fisheries & Aquaculture

Aquarium History

The origins of aquarium keeping have been around for about as long as keeping food fishes,
although the methodology and understanding of aquarium filtration has varied considerably. The
origins of aquaculture mostlikely originated when fish were trapped in some type of enclosure
after monsoon floods receded.

The earliest known aquarists were the Sumerians, who kept fishes in artificial ponds at least
4,500 years ago; records of fish keeping also date from ancient Egypt and Assyria. The Chinese,
who raised carp for food as early as 2000 BC, were probably the first to breed fish with any
degree of success. Their selective breeding of ornamental goldfish was later introduced to Japan,
where the breeding of ornamental carp was perfected. The ancient Romans, who kept fish for
food and entertainment, were the first known marine aquarists; they constructed ponds that were
supplied with fresh seawater from the ocean.

Although goldfish were successfully kept in glass vessels in England
during the middle 1700s, aquarium keeping did not become well
established until the relationship between oxygen, animals, and plants
became known a century later. During the mid 1800’s the "Balanced
Aquarium" approach was considered the only method for keeping
aquarium fish. The Balanced Aquarium consisted of "a tank in which
the air surface of the water, aided by plants would supply sufficient
oxygen" and "most of the waste from the fish was consumed by the plants and scavengers ".
By 1850 the keeping of fishes, amphibians, and reptiles had become useful in the study of nature.
It was in the works of Philip Gosse, a British naturalist, that the term aquarium first appeared. His
work aroused increased public interest in aquatic life. The first display aquarium was opened to
the public in 1853 at Regent's Park in London. It was followed by aquariums in Berlin, Naples,
and Paris. P.T. Barnum, the circus entrepreneur, recognized the commercialpossibilities of living
aquatic animals and, in 1856, opened the first display aquarium at the American Museum in New
York City as a private enterprise.

During the early 1900’s Aeration, Particulate and Charcoal filtration was touted as the state-of-
the-art but it wasn’t until the 1950’s that the Undergravel Filter was introduced. Ironically even
though it was promoted as a biological filter its true role in filtration was still misunderstood, and
yet the Undergravel Filter has been the greatest advancement to the aquarium industry.
By 1928 there were 45 public or commercial aquariums throughout the world, but growth then
slowed and few new large aquariums appeared until after World War II.
Many of the world's principal cities now have public aquariums as well as commercial ones.

It wasn’t until 1974 that successful commercial attempts to spawn and
rear marine ornamental fish began to occur and by 1975 Martin Moe and
Chris Turk of Aqualife Research and Frank Hoff and Tom Frakes of
Instant Ocean Hatcheries were raising three species of clownfish,
Oscellaris (Amphiprion ocellaris), the Tomato (A.frenatus) and the Clarki
Clownfish (A.clarkii).

In 1984 the second greatest advancement occurred in the aquarium
industry, the introduction to the US of the European Wet - Dry Filter. Now
hobbyists could keep fish as well as corals and invertebrates

Fish Through the Ages

Scientists learn how fish developed by studying the fossils of fish that are now extinct. The fossils
show the changes that occurred in the anatomy of fish down through the ages.

                                         The First Fish

The first fish appeared on the earth about 500 million years ago. These fish are called
ostracoderms. They were slow, bottom-dwelling animals that were covered from head to tail with
heavy armour of thick bony plates and scales. Like today's lampreys and hagfish, ostracoderms
had no jaws and had poorly formed fins. For this reason, scientists group lampreys, hagfish, and
ostracoderms together. Ostracoderms were not only the first fish, but also they were the first
animals to have a backbone. Most scientists believe that the history of all other vertebrates can
be traced back to the ostracoderms. The ostracoderms gave rise to jawed fish with backbones,
and they in turn gave rise to amphibians (vertebrates that have legs and live both on land and in
water). The amphibians became the ancestors of all land vertebrates.

Ostracoderms probably reached the peak of their development about 400 million years ago.
About the same time, two other groups of fish were developing - acanthodians and placoderms.
The acanthodians became the first known jawed fish. The placoderms were the largest fish up to
that time. Some members of the placoderm group called Dinichthys grew up to 30 feet (9 meters)
long and had powerful jaws and sharp bony plates that served as teeth.

The Age of Fishes

The Age of Fishes was a period in the earth's history when fish developed remarkably. Scientists
call this age the Devonian Period. It began about 410 million years ago and lasted about 50
million years. During much of this time, dinichthys and other large placoderms ruled the seas.

The First Bony Fish

The first bony fish appeared early in the Devonian period. They were mostly small or medium-

sized and, like all fish of that time, were heavily armoured. These early bony fish belonged to two
main groups - sarcopterygians and actinopterygians.

The sarcopterygians had fleshy or lobed fins. Few fish today are even distantly related to this
group. The coelacanth and the lungfish are the only surviving sarcopterygians. In addition, certain
scientists include the African bichir in this group. Some scientists believe that among fish, lungfish
are the nearest living relatives of land vertebrates. The actinopterygians had rayed fins without
fleshy lobes at the base. Among the first actinopterygians were the chondrosteans, which differed
in many ways from modern ray-finned fish. The chondrosteans were the ancestors of today's ray-
finned fish, which make up about 95 per cent of all fish species. The paddlefish and sturgeons are
the only surviving chondrosteans, and most scientists believe the bichirs are their nearest
The first sharks appeared during the Devonian Period. They looked much like certain sharks that
exist today. The first rays appeared about 200 million years after the first sharks. By the end of
the Devonian Period, nearly all jawless fish had become extinct. The only exceptions were the
ancestors of today's lampreys and hagfish. Some acanthodians and placoderms remained
through      the    Devonian     Period,      but    these  fish    also    died     out   in     time.
The first modern fish, or teleosts, appeared during the Triassic Period, which began about 240
million years ago. The chondrosteans of the Devonian Period had given rise to another group of
primitive bony fish, the holosteans. The holosteans, in turn, became the ancestors of the teleosts.
The      only     surviving     holosteans       are    the   bowfin      and     freshwater      gars.
The teleosts lost the heavy armour that covered the bodies of most earlier fish. At first, all teleosts
had soft-rayed fins. These fish gave rise to present-day catfish, minnows, and other soft-finned
fish. The first spiny-finned fish appeared during the Cretaceous Period, which began about 138
million years ago. These fish were the ancestors of such highly developed present-day fish as
perch and tuna. Since the Cretaceous Period, teleosts have been by far the most important group
of fish.


   The aquarium must be set up well in advance of the purchase of the livestock. This is a phase
requiring utmost care and imagination. If you propose to build the aquarium yourself you will
require, apart from the aquarium materials, a small screw driver, pliers, scissors, a pair of metal
shears, a glass cutter, a small hammer, and a tube of aquarium sealant.

The fish tank

     Tanks are available in various sizes and types. They can also be custom made to suit the
situation proposed for the aquarium to be kept. Before setting up, the tanks should be checked
thoroughly for leaks. If a leak is found the tank should be emptied, dried and sealed using
silicone-rubber sealant around the internal seams. If the tank drips only occasionally, there is a
good chance that it will seal itself before very long. New tanks of putty-glazed, iron-frame
construction will tend to squeeze out excess putty as the water pressure builds up, pushing the
glass panels further into the frame; this excess putty can be removed with a knife.


     Selection and preparation of gravel should be done with due consideration owing to the
following points

      Size and degree of coarseness - The particle size of the gravel is important. Too coarse
or too fine gravel should be avoided. A medium size gravel of 3 mm might be ideal. Coarse
gravel is unsuitable for two reasons. Food will quickly fall beyond the reach of the fishes and will
decay, beginning a pollution risk and if biological filtration is used, coarse gravel will not provide
enough surface area for the bacteria to colonize and the water flow through the gravel will be too
fast. If the gravel is too fine, it will pack down too tightly, under these conditions, the plant roots
will have difficulty in penetrating the gravel, and the water flow rate through a biological filter will
be severely impeded.

  Presence of calcium salts: Gravel dredged up off shore will contain many fragments of
calcium-rich seashells, which will harden the water over a period of time. A better option will be to
purchase lime-free gravel, which is available with many aquarium dealers.

  Type of gravel: Natural gravel available indigenously is the best option. Colored gravel
available with many dealers might have the obvious disadvantage of permitting the leaching of
the dye, which might have toxic effects.


   Rocks are an important adduct to the setting of an aquarium. They give a natural ambience in
that they simulate the native environment of the fishes. In a tank the fishes tend to spend most of
their time in the vicinity of these rocks. Rocks to be used in the tank should be chosen with care
considering their size, shape, contour, arrangement and chemical nature. Sharp edges can
cause injury to the fishes as they swim about. The rocks should not be erected in precarious,
overhanging poles. Calcareous rocks cause hardening of water and are hence unsuitable for a
fresh water aquarium. So are corals for the same reason. However, the water hardening rocks
may be valuable in aquariums containing fishes that tolerate hard water, such as the rift valley
lake species. Examples of suitable rocks for aquarium use are granite, basalt, quartz, and slate.
Crumbly sandstone and rocks carrying metal ore should not be used. The best choice usually is
to collect rocks from our own streams. These have aged for years in the water and have their

rough surfaces tempered by the water flow. For these reasons, they go well in all counts with the
conditions of the aquaria.

    Note: If the color of the rock work does not blend with the color of the gravel, there is an easy
trick to match the two colors, some of the rock can be smashed up into small pieces that are then
scattered on the surface of the gravel. Wrap the rock in a piece of cloth before smashing it, to
stop flying splinters and to collect the pieces all in one operation.

Wood and other decorations

     Wood is a favorite material for furnishing the aquarium naturally. Sunken logs and twisted
roots are notable features in a well-appointed aquarium. Such material can be collected from
rivers, marshes, and forests the only reservation being that any wood obtained this way must be
long dead, with no traces of rotting. Wood intended for aquarium use must be boiled in several
changes of water and immersed in water for several weeks until completely water logged, then it
may be considered fit for use. There should be no sign of discoloration of the water from the
tannins in the wood. Alternatively, dead wood can be sealed with several coats of polyurethane
varnish. Another suitable natural material is cork bark, often used as a backdrop or to form
terracing. The color is most pleasing, and it is easily cut to shape.


   The following parameters of water to be filled in the aquarium should be strictly monitored and
taken care of.

   1. Chlorine: Ordinary tap water is usually chlorinated. Since chlorine is toxic to fishes, it has to
be removed prior to introduction of fishes. Continuous aeration is the easiest and most
convenient way to do this. It has to be remembered that water used for partial exchange should
also be dechlorinated before addition to the tank.

   2. pH: A range of 6.5 to 7.5 is suitable for most tropicals. Some African Rift Lake cichlids
prefer a high pH level, while other tropicals such as tetras and rasboras prefer a lower pH level,
especially for spawning. The pH of the water has to be monitored continually and adjusted to the
levels conducive to the fishes grown. pH meters are commercially available             along with
chemicals that can bring the pH to acceptable levels.

   3. Hardness: Hardness of water is a measure of the dissolved salts of calcium and
magnesium. A concentration below 50 ppm is considered soft water where as a level above 200
ppm is considered hard water. Most tropical fresh water fish prefer to subsist in soft water.


   The plants must have an adequate depth of gravel to its root. If biological filtration is to be
used, at least 2 to 3 in (5 to 7.5 cm) of gravel must be placed over the filter plate to avoid any
adverse effects on plant growth.

Synthetic substitutes for decoration

    Synthetic substitutes for natural wood are currently available. They are usually molded from
natural logs and soon get coated with algae from the tank to become indistinguishable from the
original substance. They serve the purpose with a reasonable degree of satisfaction. Imitation
plants are also available in extremely life like replicas, which simulate not just the appearance,
but the texture, feel as also the wet drenched look of the many popular aquarium plants. These

bring a touch of greenery to any aquarium in which boisterous fishes or those with vegetarian
dietary habits are to be kept. Yet they are obviously incapable of performing the vital water
cleansing function of natural plants. In short these artificial substitutes cannot be expected to
perform the same chemical and biological processes as their living counterparts, but they can
provide shelter and spawning sites, soon disguised by a covering of natural algae.

Types of Tanks

Regardless of shape, the two basic materials used in construction are glass and acrylic. There
are advantages and disadvantages to each type.

All-Glass Tanks

The most readily available types of glass tanks are constructed entirely of glass.
Capacity varies from 10 or less gallons (37.8 L) to hundreds of gallons. All glass
tanks are constructed of plate glass, held together by a non-toxic silicone adhesive.
The thickness of the glass increases substantially as
the size of the tank increases. The entire tank is then
framed with plastic moldings for a finished
appearance. The moldings vary; many are finished in
either black or a simulated wood grain. Depending on
the manufacturer, the upper molding might include an
inside rim, which allows support for a cover glass to
minimize evaporation.

All glass tanks may be used for either for saltwater
orfreshwater fish. Never use an aquarium that is
constructed of any type of metal - not even stainless
steel, which was once widely used in aquariums. Water
salts will readily corrode metals. The metal salts
formed are highly toxic to fish. All-glass aquariums are
readily available, long-standing, and they contain no toxic materials. The only
disadvantage is that large-sized aquariums are very heavy because of the increased
glass      thickness       required        to     withstand     water      pressure.
Small all-glass tanks can be constructed using five precut panes of high-strength
glass and silicone adhesive. This is not recommended, however, because poorly
constructed tanks will not hold water or, if scaled improperly, can develop leaks.
When you select your aquarium, inspect all parts to unsure that there are no cracks
in any of the glass panes. Closely inspect the inside seams to ensure that there is a
continuous seal of silicone cement. An irregular seal of cement along the seams
eventually could cause leaks.

                Acrylic Tanks

Acrylic plastics are quite strong and can be molded into various shapes. The acrylic pieces that
form such tanks are joined with a solvent bonding cement. Many of these aquariums feature
curved front corners that make a beautiful showpiece. Acrylic aquariums are available in various
sizes and shapes, most commonly rectangular, square, or hexagonal.

The advantages of acrylic are that it is relatively lightweight, crack resistant, and it permits better
front viewing of the fish because of the tank's curved front corners. Acrylic can easily be
scratched by cleaning objects or pieces of gravel - a minor disadvantage. However, an aquarist
who is careful while cleaning the aquarium will seldom cause serious damage.

The most important pieces of the aquarium equipment are the filters, responsible for the
purification of the aquarium water. Various types of filtration equipment are available, each
performing single or multiple functions. Some filter equipment is optional, while others are an
absolute necessity for purifying the aquarium water.

When properly set up, aquariums require minimum maintenance; however, regular preventive
checks of equipment are needed to ensure proper functioning of the entire aquatic system.
Weekly and monthly maintenance tasks are required. In addition, a series of daily checks should
be made, especially during the first few weeks after the first aquatic animals have been added.
Routine daily inspection of the aquarium system ensures that problems can be found quickly and
corrected before they place the fish in jeopardy.

As a safety procedure, whenever working with aquarium equipment, make sure that the
apparatus is disconnected from electric outlets. Water is highly conductive and can transmit
dangerous electric shocks. This is especially true when working on lighting elements or adding
water to the aquarium.

It is also important to make sure that your hands are free of detergents or any other substance
that could be toxic to the fish. If you need to remove an item from the aquarium, first wash your
hands and arms well with clear warm water. Any products you use to clean the aquarium must
also be free of detergent residues or other possibly toxic materials. It is recommended that you
purchase brushes, sponges, buckets, and other items that will be used only in the maintenance of
your aquarium.

What's Inside

       Daily Maintenance
       Weekly and Monthly Maintenance

Daily Maintenance

A series of checks should be made every day to ensure that everything in the aquarium is
functioning properly. In addition to turning on the aquarium light and feeding your fish, you should
also routinely remove any food material or other debris that is visible on the substrate. You should
also account for all fish and invertebrates and observe their overall condition and behaviour.

Filters, Heaters, and Other Equipment

The next daily check involves the functioning of the filters, lighting, heaters, air stones, protein
skimmers, and other apparatus.

Filters: The undergravel filter should be examined to ensure that the proper amount of air is
flowing to operate the lift tubes. If the airflow appears diminished, it could be caused by a faulty
air pump, clogging of the air line by accumulation of salts, or clogging of the air diffuser in the
undergravel lift tube. Salt accumulation is not unusual in aquariums that have been in operation
for several months or more. The salt can be removed by passing a fine wire down the plastic air
tube in the filter to break up the salt accumulation. If this is not effective, it may be necessary to
detach the filter tube assembly from the undergravel filter and soak the parts in warm water to
dissolve the salt deposits.

Other filters, including an outside filter or canister filter, should be examined to ensure that they
are operating properly. If you notice a diminished water flow, this indicates that the filter medium
has become clogged with particulate matter and debris and requires servicing. Diminished flow
could also be caused by a crimp in the hoses of the filter.

The light bulbs should be inspected for any signs of malfunction and replaced if necessary.

Heater: The aquarium heater should then be checked to make sure it is operating properly and
the aquarium water temperature is within the acceptable range. A properly functioning heater
keeps water temperature within the set range. A slight fluctuation is acceptable and will not harm
the inhabitants. If the aquarium water is cooler than desired, adjust the heater control knob or dial
accordingly. Do this gradually, following the instructions provided by the manufacturer of the
heater. A safe approach is to turn the heater dial until the thermostat light just comes on, then
wait    several      hours,    check     the    temperature,     and     readjust    as    required.
Protein Skimmer: If your aquarium is equipped with a protein skimmer, check to see if it is
operating properly. If necessary, adjust the airflow to the skimmer. Empty the organics and waste
that have accumulated in the collecting vessel.

Air Stones: Finally, check to make sure that the air stones are operating properly. As with
undergravel filters, air stones can become clogged over time as they accumulate dirt and salts. If
you notice a decreased air flow, it may be necessary to remove the air stone and to clean it well
in fresh water. A decrease in airflow can be caused by crimped air line tubing, improperly
adjusted air valves, faulty air pump, or salt accumulation.

Water Condition and Quality: The condition and quality of the water should also be examined
daily. In a properly maintained aquarium, the water should be crystal clear and should smell
fresh. Questionable odours could indicate the need for a water change. Water deterioration could
be due to improper filtration, decaying food, or a dead fish or invertebrate.


Daily inspection of the fish in your aquarium ensures that they are accounted for and in good
health. This is best done during feeding when the majority of the fish swim in the open. If you do
not readily see a certain fish, do not assume that it has died. Since the behaviours of fish differ,
some may not readily come into the open. For example, squirrelfish tend to hide during the day
and feed during the night. However, most healthy fishes, including squirrels, soon adapt to the
feeding schedule, whatever it may be.

If you do not see a particular fish for several days, examine the aquarium closely, as it may have
died. It is also possible that it jumped out of the tank if there was an opening in the aquarium
cover. This is not uncommon, especially with certain species, such as jawfish. First, look on the
floor around the aquarium. If you do not find the fish, it will be necessary to move the rocks and
other decorations in the aquarium to locate it. You should do this carefully and with as little
disturbance as possible to the other fish.

In addition to checking for the presence of the aquarium inhabitants, you should note their
general condition every day. You should examine the fish to see if they are behaving normally.
Abnormal signs such as an increase in respiration, scratching on the aquarium bottom, or frayed
fins can indicate deterioration in water quality, aggression by tankmates, or the onset of disease.

Water Testing

Besides a general observation of water clarity, water tests including pH, ammonia, salinity, or any
other tests should be performed as required for routine weekly maintenance. Water tests need
not be performed daily except during the initial establishment of the biological filter or when new
fish are added to the aquarium.

Weekly and Monthly Maintenance

Water Changes

Regular water changes are fundamentally important in any aquarium. Even though aquarium
water is filtrated to remove toxic components, various organic and inorganic compounds
accumulate in the water over time. In fact, if an aquarium is left without any water changes,
radical alternations in the chemical composition will adversely affect the aquarium inhabitants.
These alternations include an increase in nitrate, decrease in pH, decrease in the buffering
capacity, increase in the concentration of phosphate, increase in organic compounds, and
reduction in various trace elements required by aquatic organisms.

Increase in Nitrate: Once an aquarium biological filter is functioning, there will be a continuous
accumulation of nitrate. Even though it has generally been accepted that nitrate is not toxic,
recent research suggests that high nitrate levels can interfere with the normal growth of fishes
and have an effect on the longevity of invertebrates.

Decrease in pH: Although several factors affect the decline of pH in aquarium water, chemical
by-products of nitrification are particularly noteworthy. As previously mentioned the nitrification

process results in an accumulation of nitrite and nitrate. However, these compounds are initially
added in the form of nitrous acid and nitric acid, which eventually become nitrites and nitrates
through neutralisation by natural buffers. As the buffer capacity of the water is reduced, an
accumulation of acids lowers the pH.

Decrease in Buffering Capacity: Natural water has compounds that buffer the water and
maintain the appropriate alkalinity. Over time, the buffering capacity of the water lessens. The
buffering compounds in the substrate eventually also become exhausted. Since synthetic salts
contain buffers, the regular replacement of water restores any diminished buffer capacity.
Increase in Phosphate: The build-up of phosphate in aquarium water also upsets the chemical
balance. Phosphates originate from the breakdown of various organic materials and accumulate
regularly. Although phosphate is not toxic at concentrations normally found in aquariums, high
concentrations will coat substrate particles and prevent the release of buffering chemicals. Partial
water changes greatly aid in reducing phosphate.

Increase in Organics: This is another problem in aquariums. However, various filter media as
well as protein skimmers will remove organics. Partial water changes also reduce the
concentration of organics and the accompanying yellow colour of the water. High concentrations
are known to inhibit the normal growth of fish.

Replacing Evaporated Water

It is important to replace evaporated water weekly to maintain the proper chemical balance.
Municipal water can be used, but in areas with extremely hard water, the continual addition of tap
water can eventually cause a chemical imbalance. Under such circumstances, distilled water
should be used alternately with tap water to minimise the possibility of chemical alteration of the
aquarium water. It must be remembered that to destroy any chlorine or chloramines, municipal
water needs to be treated with a water conditioner prior to addition to the aquarium.

Cleaning Aquarium Surfaces and Equipment

At least once weekly, all aquarium equipment should be wiped with a clean cloth. This should be
done especially on areas where salt has accumulated, including the aquarium cover, hood, and
sides of the aquarium. With removable aquarium covers, the easiest way to clean off collected
salt and dust is to remove the cover and scrub it under warm running water.
The outside and inside glass should also be cleaned. The outside of the aquarium can be wiped
with a cloth and a little glass cleaner. Be careful to use only a small amount of the cleaner and
never use it on the top of the tank where it could get into the water.

The inside glass can be cleaned using various manufactured devices for removing a build-up of
algae. One popular device is the cleaning magnet. Two magnets are equipped with special
nonabrasive cleaning surfaces. One magnet is placed inside the aquarium and another on the
outside. The magnetic force holds them in place. You simply move the outside magnet, which
moves the inside magnet to remove attached algae. If the inside magnet accidentally detaches
during cleaning, remove the inside magnet, rinse the cleaning surface, and inspect for any small
stones. If this is not done, remaining sand or gravel will scratch the inside surface of the
aquarium. This is especially important when cleaning acrylic tank surfaces, which damage easily.
Aquarium glass can also be cleaned with algae scrapers or cleaning sponges. The first device
uses razorblades attached to a long handle. The movement of the cleaning head scrapes algae
off the glass. The sponge type has a sponge, attached to a long handle that will also remove
algae from the glass. As with the cleaning magnets, you will avoid damage to the aquarium by

frequently inspecting the cleaning head of either device to make sure small particles or stones are
not trapped.

Cleaning Decorative Aquarium Items

Generally, there is little or no need to clean the various decorative items used in the aquarium.
Algae will grow on various rocks, coral, and shells, in time giving the aquarium a more natural
appearance. In addition, small invertebrates will begin colonising these areas. From time to time,
however, the aquarist may wish to clean off excessive growths of algae or accumulated dirt and
sediment from coral and shells. These items can be removed, cleaned, and rinsed with a small
clean toothbrush in fresh water. Never use any type of cleaning solvent or detergent to clean
decorative items. These products are toxic to fish. Decorative items generally need to be cleaned
only once every three to four months.

Cleaning Aquarium Filters

The various types of filters used in aquariums require maintenance to ensure performance.
Depending on the filter type, maintenance needs to be done anywhere from every 3 to 12 weeks.
You should follow the manufacturer's instructions for the cleaning of filters and replacement of
Undergravel Filters: Since these filters utilise the aquarium gravel as their filter medium, the
layers of the filter bed can become laden with debris. If the filter bed becomes clogged, the filter
will not function properly. Therefore, it is important to gradually stir up the top layer of the filter
bed once every few weeks to dislodge particles and ensure a uniform flow of water through the
filter bed. The debris that is stirred up will be removed by an outside filter.
If the undergravel filter bed is heavily laden with organic materials, use a special siphon cleaner
that removes water as it cleans the top surface of the filter bed. This process can be followed
once every four to six weeks or as required. The frequency is lessened when the aquarium is
equipped with an additional outside filter.

Outside Filters: These filters, including canister filters, require cleaning every four to eight
weeks, depending on the biological load in your aquarium. This entails removal and replacement
of the activated carbon and filter floss. Always retain a portion of the old floss and add to the new
floss. This ensures that some of the filter bacteria are retained in the filter. When replacing
activated carbon, rinse it with tap water to remove fine dust particles prior to placement in the

Water Testing

A series of water tests should be performed weekly or monthly. This assures that the water
quality       remains        within    acceptable        ranges     for       each        parameter.
A weekly pH test is mandatory for all freshwater aquariums. A pH test will determine if the
acceptable range is within 6.5 to 7.5. The pH will decrease over time and therefore must be
monitored. If the pH has decreased, it will be necessary to make an immediate partial water
A nitrate test should also be made weekly. The accumulation of nitrate is determined by various
factors, including the initial number of fish in the aquarium, amount of food fed, type of filtration
system, and extent of algae in the aquarium. Since algae utilise nitrogen compounds, aquariums
with an abundant growth of algae will not accumulate nitrate as rapidly as those with little or no
algae. Excessive concentrations of nitrate in the water, while not directly toxic, can interfere with
the normal growth and longevity of fish and invertebrates. Invertebrates generally do not tolerate
excessive concentrations of nitrate in the water.

Other tests, including those for ammonia, nitrite, and dissolved oxygen, are seldom required once
the aquarium is functioning properly and has undergone the conditioning period. The only
exception that would necessitate more frequent testing would be if a substantial modification is
made to the aquarium system-for example, the addition of a new filter, a complete cleaning of the
filter systems, a change in the type and amount of food fed, or the addition of several new fish.


Tank Location

Where the aquarium is placed is a matter of personal preference. It makes a beautiful focus in a
living room, den, bedroom, or any other room. Larger aquariums can be placed as an attractive
room divider. Wherever you decide to situate the aquarium, it is important to have easy access to
multiple wall outlets to minimise the use of extension cords.

The aquarium should not be placed either in an area subject to cold drafts or in one that is
excessively warm. Do not place the aquarium too close to a radiator, air conditioner, or directly in
front of a window that receives strong sunlight. While several hours of sunlight are beneficial to
aquariums, strong sunlight can promote excessive algae growth as well as overheating in small
aquariums. This is particularly dangerous in the summer months.

The selection of an aquarium stand or cabinet has previously been discussed . Regardless of the
type of aquarium support, make sure that the aquarium is level to avoid unnecessary stress on
parts of the aquarium. This is especially important for all-glass aquariums.


The substrate - material to cover the aquarium bottom -should be selected carefully. Some
bottom materials used in freshwater aquariums are not suitable for an aquarium. Freshwater
aquariums often use quartz gravel, epoxy-coated rock, or similar materials, many of which are
dyed various colours. From an aesthetic point of view, coated or coloured bottom substrates
should never be used in aquariums. Coloured substrates detract from the overall natural beauty
of the aquarium and especially from the striking coloration of the fish.

Only substrates with a calcareous composition should be used for aquariums, since they are the
only type that has the capability of buffering the water. The most commonly available appropriate
substrates include natural coral sand, limestone, oyster shell, and dolomite. A combination of
calcareous materials can also be used for aquascaping the aquarium bottom.
Aquarium bottom materials are essential for proper biological and mechanical filtration when an
undergravel filter is used. Large-sized grains of substrate should be avoided, as they
inadequately perform mechanical and biological filtration. They also have a substantially reduced
surface area compared to smaller-sized particles. This means that there is less area for the
beneficial nitrifying bacteria to grow on. On the other hand, very small grains of material such as
sand must never be used to cover the aquarium bottom. Sand will rapidly clog undergravel filters
and prevent a uniform flow of water through the filter plate. The general recommendation is to
select a grain size of 0.12 to 0.2 inches (3 to 5 mm). If no undergravel filter is used, virtually any
size of calcareous material can be used to cover the aquarium bottom.

Amount of Required Substrate

The amount of material for an aquarium is mainly dependent on whether you are using an
undergravel filter. It is highly recommended that you include an undergravel filter as standard
equipment for your first aquarium.

With an undergravel filter a recommended depth of bottom material is 2.5 to 3.0 inches (6.3 to 7.6
cm). This will ensure that you have ample material for proper filtration through your biological
filter. You may make the bottom material deeper, but do not make it less than the stated
In aquariums without an under-gravel filter, a shallow layer of substrate is all that should be used
to cover the bottom, with a depth of not more than 1/2 to 3/4 of an inch (1.2 to 3 cm) of substrate.
The size substrate in this situation is not as critical as with aquariums with undergravel filtration.
Without an undergravel filter, the bottom material depth must be restricted to minimise the
possibility of anaerobic bacterial activity. These bacteria develop in filter beds where there is
restricted water flow to carry dissolved oxygen. Without a constant water flow through a filter bed,
the substrate favours the growth of anaerobic bacteria, producing toxic gases such as methane
and hydrogen sulphide. Both of these gases, even in very low concentrations, are poisonous to
aquatic animals.


                       External Anatomy


Most fish have a streamlined body. The head is somewhat rounded at the front. Fish have no
neck, and so the head blends smoothly into the trunk. The trunk, in turn, narrows into the tail.
Aside from this basic similarity, fish have a variety of shapes. Tuna and many other fast
swimmers have a torpedolike shape. Herring, freshwater sunfish, and some other species are
flattened from side to side. Many bottom-dwelling fish, including most rays, are flattened from top
to bottom. A number of species are shaped like things in their surroundings. For example,
anglerfish and stonefish resemble rocks, and pipefish look like long, slender weeds. This
camouflage, called protective resemblance, helps a fish escape the notice of its enemies and its

Skin and colour

Most fish have a fairly tough skin. It contains blood vessels, nerves, and connective tissue. It also
contains certain special cells. Some of these cells produce slimy mucus. This mucus makes fish
slippery. Other special cells, called chromatophores or pigment cells, give fish many of their
colours. A chromatophore contains red, yellow, or brownish-black pigments. These colours may
combine and produce other colours, such as orange and green. Some species have more
chromatophores of a particular colour than other species have or have their chromatophores
grouped differently. Such differences cause many variations in colouring among species. Besides
chromatophores, many fish also have whitish or silvery pigments in their skin and scales. In
sunlight,    these      pigments     produce      a   variety    of    bright    rainbow      colours.
The colour of most fish matches that of their surroundings. For example, most fish that live near
the surface of the open ocean have a blue back, which matches the colour of the ocean surface.
This type of camouflage is called protective coloration. But certain brightly coloured fish, including
some that have poisonous spines, do not blend with their surroundings. Bright colours may
protect a fish by confusing its enemies or by warning them that it has poisonous spines.
Most fish can change their colour to match colour changes that are present in their surroundings.
Flatfish and some other fish that have two or more colours can also change the pattern formed by
their colours. A fish receives the impulse to make such changes through its eyes. Signals from a
fish's nerves then rearrange the pigments in the chromatophores to make them darker or lighter.
The darkening or lightening of the chromatophores produces the different colour patterns. Scales.
Most jawed fish have a protective covering of scales. Teleost fish have thin, bony scales that are

rounded at the edge. There are two main types of teleost scales - ctenoid and cycloid. Ctenoid
scales have tiny points on their surface. Fish that feel rough to the touch, such as bass and
perch, have ctenoid scales. Cycloid scales have a smooth surface. They are found on such fish
as carp and salmon. Some primitive bony fish, including bichirs and gars, have thick, heavy
ganoid scales. Sharks and most rays are covered with placoid scales, which resemble tiny,
closely spaced teeth. Some fish, including certain kinds of eels and fresh-water catfish, are


Fins are movable structures that help a fish swim and keep its balance. A fish moves its fins by
means of muscles. Except for a few finless species, all modern bony fish have rayed fins. Some
primitive bony fish also have rayed fins. These fins consist of a web of skin supported by a
skeleton of rods called rays. Some ray-finned fish have soft rays. Others have both soft rays and
spiny rays, which are stiff and sharp to the touch. Some primitive bony fish have lobed fins, which
consist of a fleshy base fringed with rays. Lobed fins are less flexible than rayed fins. Sharks,
rays, and chimaeras have fleshy, skin-covered fins supported by numerous fine rays made of a
tough material called keratin.

Fish fins are classified according to their position on the body as well as according to their
structure. Classified in this way, a fin is either median or paired.

Median fins are vertical fins on a fish's back, underside, or tail. They include dorsal, anal, and
caudal fins. The dorsal fin grows along the back and helps a fish keep upright. Almost all fish
have at least one dorsal fin, and many have two or three. The anal fin grows on the underside
near the tail. Like a dorsal fin, it helps a fish remain upright. Some fish have two anal fins. The
caudal fin is at the end of the tail. A fish swings its caudal fin from side to side to propel itself
through the water and to help in steering.

Paired fins are two identical fins, one on each side of the body. Most fish have both pectoral and
pelvic paired fins. The pectoral, or shoulder, fins of most fish grow on the sides, just back of the
head. Most fish have their pelvic, or leg, fins just below and behind their pectoral fins. But some
have their pelvic fins as far forward as the throat or nearly as far back as the anal fin. Pelvic fins
are also called ventral fins. Most fish use their paired fins mainly to turn, stop, and make other

Kinds of fish scales

These drawings show examples of the four main types of fish scales. Most modern bony fish
have ctenoid or cycloid scales. Some catfish and a few other species have no scales at all.

     Ctenoid scale                                               Cycloid scale

     Ganoid scale                                                Placoid scale

Internal Anatomy

Skeleton and muscles

The skeleton of fish

The skeletons of most fish consist mainly of (1) skull, (2) a backbone, (3) ribs, (4) fin rays, and (5)
supports for fin rays or fins. The skeleton of a yellow perch is shown below.
A fish's skeleton provides a framework for the head, trunk, tail, and fins. The central framework
for the trunk and tail is the backbone. It consists of many separate segments of bone or cartilage

called vertebrae. In bony fish, each vertebra has a spine at the top, and each tail vertebra also
has a spine at the bottom. Ribs are attached to the vertebrae. The skull consists chiefly of the
brain case and supports for the mouth and gills. The pectoral fins of most fish are attached to the
back of the skull by a structure called a pectoral girdle. The pelvic fins are supported by a
structure called a pelvic girdle, which is attached to the pectoral girdle or supported by muscular
tissue in the abdomen. The dorsal fins are supported by structures of bone or cartilage, which are
rooted in tissue above the backbone. The caudal fin is supported by the tail and the anal fin by
structures of bone or cartilage below the backbone.

Like all vertebrates, fish have three kinds of muscles: (1) skeletal muscles, (2) smooth muscles,
and (3) heart muscles. Fish use their skeletal muscles to move their bones and fins. A fish's flesh
consists almost entirely of skeletal muscles. They are arranged one behind the other in broad
vertical bands called myomeres. The myomeres can easily be seen in a skinned fish. Each
myomere is controlled by a separate nerve. As a result, a fish can bend the front part of its body
in one direction while bending its tail in the opposite direction. Most fish make such movements
with their bodies to swim. A fish's smooth muscles and heart muscles work automatically. The
smooth muscles are responsible for operating such internal organs as the stomach and
intestines. Heart muscles form and operate the heart.

Systems of the body

The internal organs of fish, like those of other vertebrates, are grouped into various systems
according to the function they serve. The major systems include the respiratory, digestive,
circulatory, nervous, and reproductive systems. Some of these systems resemble those of other
vertebrates, but others differ in many ways.

Respiratory system

Unlike land animals, almost all fish get their oxygen from water. Water contains a certain amount
of dissolved oxygen. To get oxygen, fish gulp water through the mouth and pump it over the gills.
Most fish have four pairs of gills enclosed in a gill chamber on each side of the head. Each gill
consists     of     two    rows    of    fleshy    filaments      attached      to    a     gill  arch.
Water passes into the gill chambers through gill slits. A flap of bone called a gill cover protects the
gills of bony fish. Sharks and rays do not have gill covers. Their gill slits form visible openings on
the outside of the body.

In a bony fish, the breathing process begins when the gill covers close and the mouth opens. At
the same time, the walls of the mouth expand outward, drawing water into the mouth. The walls
of the mouth then move inward, the mouth closes, and the gill covers open. This action forces the
water from the mouth into the gill chambers. In each chamber, the water passes over the gill
filaments. They absorb oxygen from the water and replace it with carbon dioxide formed during

the breathing process. The water then passes out through the gill openings, and the process is

Digestive system

Digestive system, or digestive tract, changes food into materials that nourish the body cells. It
eliminates materials that are not used. In fish, this system leads from the mouth to the anus, an
opening in front of the anal fin. Most fish have a jawed mouth with a tongue and teeth. A fish
cannot move its tongue. Most fish have their teeth rooted in the jaws. They use their teeth to
seize prey or to tear off pieces of their victim's flesh. Some of them also have teeth on the roof of
the mouth or on the tongue. Most fish also have teeth in the pharynx, a short tube behind the
mouth.         They      use       these        teeth      to      crush     or      grind      food.
In all fish, food passes through the pharynx on the way to the esophagus, another tubelike organ.
A fish's esophagus expands easily, which allows the fish to swallow its food whole. From the
esophagus, food passes into the stomach, where it is partly digested. Some fish have their
esophagus or stomach enlarged into a gizzard. The gizzard grinds food into small pieces before it
passes into the intestines. The digestive process is completed in the intestines. The digested food
enters the blood stream. Waste products and undigested food pass out through the anus.

Circulatory system

Circulatory system distributes blood to all parts of the body. It includes the heart and blood
vessels. A fish's heart consists of two main chambers - the atrium and the ventricle. The blood
flows through veins to the atrium. It then passes to the ventricle. Muscles in the ventricle pump
the blood through arteries to the gills, where the blood receives oxygen and gives off carbon
dioxide. Arteries then carry the blood throughout the body. The blood carries food from the
intestines and oxygen from the gills to the body cells. It also carries away waste products from the
cells. A fish's kidneys remove the waste products from the blood, which returns to the heart
through the veins.

Nervous system

Nervous system of fish, like that of other vertebrates, consists of a spinal cord, brain, and nerves.
However, a fish's nervous system is not so complex as that of mammals and other higher
vertebrates. The spinal cord, which consists of soft nerve tissue, runs from the brain through the
backbone. The brain is an enlargement of the spinal cord and is enclosed in the skull. The nerves
extend from the brain and spinal cord to every part of the body. Some nerves, called sensory
nerves, carry messages from the sense organs to the spinal cord and brain. Other nerves, called
motor nerves, carry messages from the brain and spinal cord to the muscles. A fish can
consciously control its skeletal muscles. But it has no conscious control over the smooth muscles
and heart muscles. These muscles work automatically.

Reproductive system

As in all vertebrates, the re-productive organs of fish are testes in males and ovaries in females.
The testes produce male sex cells, or sperm. The sperm is contained in a fluid called milt The
ovaries produce female sex cells, or eggs. Fish eggs are also called roe or spawn. Most fish

release their sex cells into the water through an opening near the anus. The males of some
species have special structures for transferring sperm directly into the females. Male sharks, for
example, have such a structure, called a clasper, on each pelvic fin. The claspers are used to
insert sperm into the female's body.

Special organs

Most bony fish have a swim bladder below the backbone. This baglike organ is also called an air
bladder. In most fish, the swim bladder provides buoyancy, which enables the fish to remain at a
particular depth in the water. In lungfish and a few other fish, the swim bladder serves as an air-
breathing lung. Still other fish, including many catfish, use their swim bladders to produce sounds
as well as to provide buoyancy. Some species communicate by means of such sounds.
A fish would sink to the bottom if it did not have a way of keeping buoyant. Most fish gain
buoyancy by inflating their swim bladder with gases produced by their blood. But water pressure
increases with depth. As a fish swims deeper, the increased water pressure makes its swim
bladder smaller and so reduces the fish's buoyancy. The amount of gas in the bladder must be in-
creased so that the bladder remains large enough to maintain buoyancy. A fish's nervous system
automatically regulates the amount of gas in the bladder so that it is kept properly filled. Sharks
and rays do not have a swim bladder. To keep buoyant, these fish must swim constantly. When
they rest, they stop swimming and so sink toward the bottom. Many bottom-dwelling bony fish
also lack a swim bladder.

Many fish have organs that produce light or electricity. But these organs are simply adaptations of
structures found in all or most fish. For example, many deep-sea fish have light-producing organs
developed from parts of their skin or digestive tract. Some species use these organs to attract
prey or possibly to communicate with others of their species. Various other fish have electricity-
producing organs developed from muscles in their eyes, gills, or trunk. Some species use these
organs to stun or kill enemies or prey.


Aquarium fish are susceptible to infectious and non-infectious diseases. Infectious diseases are
caused by biological agents such as bacteria or protozoas that attack susceptible fish, reproduce,
and are then transmitted to other fish. Non-infectious diseases are nontransmissible and can be
caused by a variety of factors, such as poor nutrition or poor water quality.
Many diseases that are unknown in fish in the natural habitat can occur in aquariums under
circumstances that favour the disease development. The immune system of healthy aquatic
animals protects them from invasion by disease agents. A minor infection can progress to clinical
disease only when the balance between the disease agent and the fish or invertebrate shifts in
favour of the disease agent.

The outbreak of disease in an aquarium is serious, especially for the new hobbyist who is
generally inexperienced in recognition and control of fish diseases. The best approach to control
is always prevention-by providing proper environmental conditions, a good program of aquarium
maintenance, a sound diet, and by the use of other preventive measures.

To prevent disease outbreaks, it is important to understand how diseases occur. Disease is a
process initiated by reduced resistance of the fish. It is a disruption of the delicate balance
involving the fish, the environmental conditions, and the disease agents. Research to date
strongly shows that the disease process can be initiated by exposure to unfavourable
environmental changes such as temperature fluctuations, persistent ammonia concentrations, low
oxygen levels, overcrowding, and inadequate diets. Each of these factors can play a role in the
initiation and development of a disease. The conditions listed above are referred to as stress
factors. These stress factors singly or in combination cause the stress response, which,
depending on the intensity and duration can be either beneficial or potentially hazardous to the

The Stress Response

Environmental stress decreases the natural resistance of a fish, making it susceptible to disease.
Stress is often thought of as negative, but the stress response is a beneficial adaptation to
unfavourable conditions.

Initially, when a fish is exposed to a stress factor (stressor), the biochemistry of the fish is altered
with the release of various hormones. These chemicals have profound effects, preparing the fish
for an emergency situation. The detailed biochemical changes accompanying the stress response
are complicated and will not be discussed here in detail; however, the result of these changes
enables the fish to cope with potentially dangerous circumstances. For example, if a fish is
subjected to stress caused by capture or transport, it will respond to the stress response with the
release of various chemicals. These chemicals cause a dilation of gill capillaries, increased blood
flow to various parts of the body, and the immediate availability of energy nutrients. Once the fish
begins to acclimate to the new aquarium conditions, the fish's body chemistry will slowly return to
normal. The physiological changes that occur during such stress episodes help the fish to survive
a potentially dangerous situation. However, prolonged exposure to such stressors as chronic
levels of ammonia in the water will have serious consequences, including interference in the
ability to fight infection.

Minimising stressful situations in aquariums is well within the reach of aquarium hobbyists
through careful management of the environment, performing recommended water maintenance,
avoiding overcrowding, and providing a superior diet. However, if disease does occur, you will
need to be able to recognise the problem and take immediate action.

Disease Recognition and Prevention

Fish should be carefully selected prior to purchase to be sure they are in good condition.
Evaluating a fish's condition is based on careful observations of the fish's behaviour and
familiarity with common disease agents. Learning how to interpret abnormal behaviours
associated with fish disease requires years of experience, but every aquarist, with some study
and practice, should be able to recognise many of the disease signs.

Disease Recognition

Sick fish alter their normal behavioural patterns in response to a disease agent or environmental
changes. Often the sign observed is not specific, but indicative of either infectious disease or non-
infectious water-quality or nutrition-related problems. Some disease signs, such as the presence
of a parasite on the fish's body, are specific and easily recognised as a sign of infectious disease.
For the inexperienced aquarist, caution must be observed in attempting to diagnose a disease
Diseased fish are recognised by various signs, including:

       increased respiration rate
       scratching on objects or the aquarium bottom
       pale coloration
       refusal to eat
       frayed fins
       appearance of body ulcers
       cloudy eyes, and other signs.

These signs do not necessarily indicate the specific cause, only that a health problem is
developing. Pale colour, for example, could be caused either by improper nutrition, the early
stages of an infectious disease, or poor water quality. Increased respiration is a sign easily
recognised, and can be in response to an environmental problem such as a low-dissolved oxygen
level or to parasites on the gills. Making a diagnosis from one sign is often very difficult. An
accurate diagnosis necessitates the gathering of various pieces of information, including water-
quality parameters, maintenance data, and close observation of the affected fish's behaviour.
The following non-specific disease signs are commonly associated with aquarium fish affected
with a disease.

Increased Respiration: Fish have an abnormally high rate of breathing, with a tendency to stay
near the water surface or areas of high water agitation.

Possible Causes: Water-quality problem such as low oxygen concentrations, high ammonia, or
high temperature are likely the cause of increased respiration; the fish could also be infested with
external parasites.

Scratching: Aquarium fish scratch or rub themselves repeatedly on objects in the aquarium or on
aquarium bottom.

Possible Causes: Continual scratching is most often associated with parasitic infestation.

Clamped Fins: The affected fish will tend to hold its fins close to the body proper. Frayed fins can
sometimes be observed.

Possible Causes: Most fish erect their fins during swimming, though this behaviour varies. Fish
that tightly clamp their fins and appear to be listless could be in the early stages of disease. If
frayed fins are also present, it could indicate that the fish has been in a fight with another fish in
the aquarium.

Lethargy: There is a decrease or lack of normal swimming or feeding activity.
Possible Causes: This can be related to infectious disease or too low water temperature. It
should not be confused with normal inactivity during sleep periods.

Lack of Appetite: This sign is common and can be caused by various factors. Affected fish
refuse to feed or abruptly stop feeding.

Possible Causes: Refusal to eat can be related to feeding an improper type of food, such as
feeding dry food to fish that accept only live foods. When fish suddenly stop feeding, it could
indicate the early stages of an infectious disease. When this occurs after the introduction of a new
aquarium fish, it can be related to the fright response or to aggression by tankmates.

Pale Colour: Fish lose their natural coloration and become pale.

Possible Causes: A short-term change in colour is normal and can be related to a fright
response. This can occur when fish are moved from one tank to another. Chronic pale colour can
be related to development of disease or poor nutrition. Chronic abnormal light colour can also
indicate blindness.

Cloudy Eyes: With this easily recognisable sign, either one eye or both eyes become cloudy.

Possible Causes: Physical injury related to capture or netting is not uncommon with new fish.
The development of a cloudy eye can also indicate physical injury caused by fighting. The
condition is sometimes temporary, while extensive physical damage can result in permanent
injury. Cloudy eyes can also be a sign of bacterial or parasitic disease.

Frayed Fins: The fins are either frayed or shredded. The base of the fins may have a reddish

Possible Causes: This can be caused by injury from fighting with tankmates, or can indicate the
early stages of a bacterial or other infectious disease.

White Spots on Body: Affected fish have irregular distribution of white spots over the body.

Possible Causes: This can be caused by external protozoan parasites or by adherence of fine
particulate matter or air bubbles in the mucus.

Ulceration of Body: Small-to-large ulcers on the body may have pale areas and reddened

Possible Causes: Ulcers may indicate bacterial infection and/or parasitic infestation.

Swollen Abdomen: The fish appears to be swollen or bloated.

Possible Causes: A swollen abdomen can be an indication of an internal bacterial infection,
parasitic infestation, or a tumour. It can also be caused by overeating in certain species of fish.

Diagnosing Diseases and Their Causes

It should now be evident that various disease signs can be caused by agents ranging from
environmental abnormalities to biological causes such as parasites. Determining the exact cause
is not always possible, but it is important to distinguish between diseases initiated by
environmental problems and those caused by disease agents.

Assume, for example, that you have an aquarium with several species of fish. You notice that one
fish has an increased respiratory rate. From the disease signs previously discussed, this could be
related to an environmental problem such as low oxygen concentration or to parasites. How do
you determine the exact cause of the increased breathing rate of the fish? It is important not to
assume immediately that the fish is infested by parasites until you are firmly convinced that the
rapid respiration is unrelated to water quality. This is due to the fact that a great majority of
problems, especially in new aquariums, are related to water quality. The recommended approach
is to first perform a series of water tests, including pH, ammonia, nitrite, and others. Check to
make sure all filters and air stones are functioning properly.

Disease Prevention

It is a basic premise that preventing diseases is the best means of control. Good aquarium-care
techniques, regular maintenance, proper nutrition, preventing overcrowding of fish and use of
quarantine aquariums will all minimise the development of disease. A quarantine aquarium is one
of the most important methods of preventing the introduction of diseases to your aquarium.


Isolating new fish in a separate aquarium is a highly effective means of preventing the
introduction of diseases to an established aquarium. Quarantine aquariums are often referred to
as "hospital aquariums" or "isolation tanks." The process of quarantine requires a separate small
aquarium that will be used exclusively for the isolation of new aquarium fish.
While a quarantine aquarium is not required during the first introduction of fish to your display
aquarium, quarantine is recommended for future additions of fish to your main aquarium. The use
of quarantine aquariums is based on the assumption that all new aquarium fish carry some type
of disease agent, especially external parasites. During capture, holding, and transport, fish are
stressed, which in turn decreases their resistance to disease. Parasites are known to multiply
rapidly during transport. If diseased fish are added directly to an established display aquarium,
they will transmit the disease agents to other fish.

Another benefit of quarantine is that it allows new fish to acclimate to their new conditions in a
less stressful environment. New fish directly added to an aquarium are often bullied by the
established fish, making it more difficult for the new fish to acclimate.

Quarantine Period

The recommended quarantine period for new fish is a minimum of three weeks. The first week is
critical, requiring frequent observation of the behaviour of your new fish. It is during the first week
that you can determine if the new fish are adjusting to their new environment. Mortalities cannot
always be avoided, since some fish species are not always capable of the needed adjustment.
Any fish found dead in the quarantine aquarium must be removed promptly to prevent increased
levels of bacteria and water pollution.

It is recommended that new fish be fed as soon as they begin to show an interest in eating. Hardy
species, such as damselfish, are usually the first to respond to the addition of food. Other
species, such as butterflyfish, tend to be more sensitive and may not eat for a few days.
However, as long as the fish were known to have been eating in the retailer's aquarium prior to
purchase, you need not be overly concerned with the initial lack of interest in food. During
quarantine, be cautious not to overfeed the new fish, but provide enough for them to obtain
adequate nourishment.

All new fish, without exception, must be placed in the quarantine aquarium. Even fish that appear
to be in perfect condition could be harbouring parasites. Once the fish are placed into quarantine,
additional fish should not be added until the initial group has completed quarantine and has been
moved to the display aquarium.

Upon completion of the quarantine period, if the fish appear healthy, they can be transferred to
your main aquarium. If not, they should remain in quarantine for an additional few weeks or more.

Quarantine Treatment Methods

New fish need to be treated with chemical preparations to eradicate possible external parasites
and to control any possible secondary bacterial infections.

It should be pointed out that while various medications are commonly used during quarantine for
treatment of fish, they should never be used for treating invertebrates. The majority of
invertebrates are extremely sensitive to chemicals, at substantially lower concentrations than
those used to treat fish.

Although a more detailed description of the appropriate chemicals will be discussed later in this
chapter, some introductory remarks are in order.

Various chemicals are available for use during quarantine to control parasitic infestations and
bacterial infections. Some of the products most widely used to control common external parasites
contain copper. These medications have been used for over three decades as the most reliable
means of eradicating serious protozoan parasites of fish.

Copper:Copper-based medications are widely available under various trade names. Make sure
that the active ingredient, noted on the label, is copper sulphate, copper sulphate pentahydrate,
or other copper compounds. Such solutions also contain additional ingredients such as citric acid.
These solutions are commonly referred to as "free copper" or "ionic copper." These differ from
other copper-based solutions that are known as "chelated copper." Chelated copper-based
products differ chemically from ionic copper. Do not purchase chelated copper medications, as
these are not as effective in eradicating parasites and can cause serious problems for your
aquarium and fish. If you are unsure of the type of copper solution to purchase, you should rely
on the advice of your pet shop retailer.

Copper can be very toxic to fish when not used properly, and no treatment should begin unless a
copper test kit is available for monitoring the copper concentration in the water. Since copper is
removed through the interaction with various chemicals in water, additional booster doses must
be added periodically to maintain the proper concentration. Although the procedure can differ
according to the copper medication used, the following is the generalised procedure for treatment
with copper.

Add the proper amount of copper solution to the aquarium water according to the label
instructions to produce a concentration of 0.12 to 0.18 mg/L (ppm). Perform a copper test every
day to ensure that the concentration is within the acceptable range. The initial concentration
should be brought up to 0.18 mg/L. It is important that the concentration not exceeds the upper
range or decrease below the lower limit. The treatment must continue uninterrupted for a
minimum of 21 days. Upon completion of the treatment, a partial water change should be made to
assist in reducing any residual copper in the water. Since copper is toxic to invertebrates, they
must never be added to the quarantine tank just after a copper treatment.

Organophosphates: In addition to copper, there are other chemicals available for controlling
parasites; copper alone is not able to control every type of parasite affecting aquarium fish.
Organophosphates or formalin-based products are recommended for eradication of worm-like
parasites called flukes, commonly present on various species of fish. The treatments can be
concurrent with the copper treatment. You should rely on your local retailer to obtain either of
these medications together with instructions for their correct use.

Antibiotics: Although external parasites are the major disease-causing agents of new aquarium
fish, it is sometimes necessary to use antibiotics to control bacterial infections. Injuries sustained
during netting, frayed fins due to aggressive behaviour with other fish, or severe external parasitic
infestation can often require treatment to prevent a serious infection. Antibiotics must be used
carefully to prevent overuse in treating every suspected bacterial infection.

Fungal, Bacterial, and Viral Diseases

Funguses, bacteria, and viruses are responsible for various diseases of aquarium fish.
Collectively, this group of disease agents are referred to as microbes. All are so small that it is not
possible to see the organism without the use of a microscope. Identification of diseases caused
by these organisms must initially rely on external signs such as lesions or nodules.
Microbial disease outbreaks in aquariums are correlated with a deterioration of water quality,
parasites that damage the fish's skin or gills, or poor nutrition. Any trauma that weakens the fish's
disease resistance barriers allows invasion by microbes. Microbial diseases are readily
transmitted from one fish to another.

Fungal Infections: Fungal infections are not uncommon in aquarium fish. Infection often follows
prior damage to a fish, caused by handling with a net or by an existing infection by parasites.
Aquarium hobbyists familiar with fungal infections of freshwater fishes will be familiar with the
characteristic white, cottonlike growth of fungus on the skin or fins of infected fish. Known as
Saprolegnia sp., this fungus readily invades stressed freshwater fish, but is not known to affect
decorative fishes. Signs of fungal infection in fish are therefore less dramatic and often difficult to
When present, the fungus appears on fishes as a fine film, dark pigmented areas, or a coating
covering areas of the body or gills. This coating can easily be confused with similar signs that are
caused by the presence of various types of parasites.

Treatment: Treatment of fungal infections of the body and gills involves the use of various
fungicides available commercially. Malachite green and methylene blue have been used
successfully to control fungal infections in decorative fish. Various drugs are also useful for
controlling both fungal and bacterial infections. Since fungus is a secondary invader, treatment
methods must also address the initial cause of the disease, including trauma induced by
deteriorated water quality, poor nutrition, or poor handling of the fish.

Bacterial infections: These are also commonly associated with preexisting trauma or stress of
fish, including poor water quality, handling trauma, and poor nutrition. Pathogenic bacteria-those
that can cause disease-as well as the beneficial nitrifying bacteria are always present in aquarium
water. The pathogenic bacteria will initiate disease only if the fish's immune system is impaired.
Providing optimal water quality, controlling the presence of parasites, and practising good
aquarium management will prevent the outbreak of bacterial diseases. The exact identification of
bacteria requires the use of sophisticated diagnostic tests routinely used by laboratory
technicians. The procedures involve growing the bacteria on specialised media, then conducting
various chemical tests.

Many bacterial infections can be identified by various signs they produce when they infect fish.
Bacterial infections can be divided into those causing external infections and those primarily
causing internal lesions. It must be noted that external infections can rapidly worsen, spreading to
the internal organs and bloodstream. Bacteria can enter fish either through the skin or by oral

External bacterial infections (fin-and-tail rot and ulcer disease) can be caused by various species
of bacteria. Bacteria most commonly associated with these infections include pseudomonas,
myxobacteria, and vibrio. The latter group is the major cause of bacterial infections, especially in
newly imported fish that are still under extreme stress from capture and transport.
Collectively, the signs of external infections caused by these bacteria are often referred to as "fin-
and-tail rot" and "ulcer" disease. The names refer to the signs of infections from bacterial disease
and not to their cause from specific bacteria.

Treatment: Bacterial infections must be treated promptly because of the rapid progression of the
disease from minor to severe. Various antimicrobials are available for treating bacterial diseases
of fish. Those recommended for the treatment of external infections of the body surface include
nitrofurazone, nifurpirinol, and various sulfonamides. Although various antimicrobials are
available commercially for the treatment of bacterial infections, not all are suitable for use in
freshwater aquariums. Those that are virtually useless for treatment of infections in aquariums
include ampicillin, penicillin, tetracycline, and erythromycin. The latter can kill the nitrifying
bacteria in your aquarium, causing an increase in toxic ammonia. In addition to treating your
aquarium, you should also investigate other possible causes of the outbreak, including the
addition of non-quarantined fish, excessively high water temperatures, an overcrowded aquarium,
low-dissolved oxygen, or other parameters that could have initiated the infection.
The signs of the disease differ with the species of fish as well as the extent of infection. Typically,
fish can develop a pronounced swelling of the body with a change in normal body coloration. The
appearance of signs associated with mycobacterio-sis is largely dependent on the stage of the
disease. Fish in advanced stages become emaciated, have swollen or cloudy eyes, and can
develop ulcers on the body.

Viruses: Decorative fish are also susceptible to infection by viruses, although few have been
identified from aquarium fish. Viruses are smaller than bacteria and require the use of
sophisticated            electron       microscopes           for         their       identification.
The major virus common among freshwater fishes and relatively easy to identify from the lesions
it produces is lymphocystis. The disease is chronic, meaning that in the majority of cases it will
not kill the infected fish. The major consequence of lymphocystis disease is disfigurement of the
The disease agent preferentially infects the cells of the skin and fins, causing the appearance of
lesions. Once the virus infects a cell, it takes over the activities of the cell, forcing it to
manufacture more viruses.

Treatment: There is no known cure for lymphocystis. The use of medications including antibiotics
appears to be useless. If the lesions are restricted to the distal area of a fin, it is possible to
carefully trim off the infected portion and treat with an antibiotic to prevent a bacterial Infection. In
many cases, however, the virus will reappear in the same area.

to will be discussed below in relation to water quality deterioration in the aquarium.

       Nitrogen Compounds: Ammonia, nitrite, and nitrate formed during the process of
        nitrification can all have serious consequences for the health of fish. Ammonia and nitrite

    pose more of a problem than nitrate the least toxic of these compounds.
    Ammonia is the most toxic to freshwater organisms. As ammonia accumulates in the
    bloodstream and in the tissues, affected organisms are unable to transport oxygen
    properly. Sensitive aquatic animals succumb rapidly to very low concentrations of
    ammonia. As we pointed out in an earlier chapter, the higher the pH and temperature, the
    greater the proportion of toxic ammonia formed.
    The accumulation of ammonia is most serious when conditioning is still in process, or
    when there is excess decaying food in the aquarium, overcrowding of fish, and/or
    inadequate filtration. Chronic ammonia concentrations will predispose fish to other
    diseases and will kill those species that are most sensitive to high ammonia
    Fish affected by ammonia poisoning will appear listless, will show an increased
    respiration rate, and can develop other opportunistic bacterial infections. An ammonia
    test must be performed if any of these signs are observed in the aquarium. In the event of
    abnormal concentrations, you should make an immediate water change to reduce the
    ammonia concentration. If the source is overcrowding, you should move some of the fish
    to another holding aquarium.

    Although nitrite is less toxic than ammonia, fish can still be harmed by the accumulation
    of this toxin. Sensitive fish such as butterflyfish will not tolerate nitrite.
    High concentrations of nitrite are generally a serious problem only during the aquarium
    conditioning period. High nitrite affects fish by preventing the normal uptake of oxygen.
    As with ammonia, the concentration of nitrite is reduced by making water changes.
    Nitrate is the least toxic of the nitrogen products, although tolerance of nitrate varies
    among species of fish. However, despite its greatly reduced toxicity, accumulations of
    nitrate are known to affect the normal growth of fish and the survivability of invertebrates.
    Regular water changes will reduce the amount of nitrate. The easiest way to control the
    build-up of excessive nitrate is to allow some controlled growth of algae in the aquarium.
    In addition, keeping the filter running efficiently, avoiding crowding of animals in the
    aquarium, as well as not overfeeding minimises the build-up of nitrate.

   Chlorine and Chloramines: All municipal water supplies are treated either with chlorine
    or chloramines to purify the water for human consumption. Chlorine has been the most
    widely used for water purification, but in recent years chloramination has been replacing
    chlorination. Detoxifying tap water to destroy chlorine has been easily accomplished by
    simply adding a chlorine remover or multipurpose water conditioners. When these are
    added, chlorine is destroyed and the water can be used safely for the aquarium.
    However, the situation is more complicated when municipal water is treated with
    Both chlorine and chloramine are toxic to fish , but chloramines differ in many respects
    from chlorine. Chloramines can be thought of as a combination of ammonia and chlorine.
    Chemically, they are very stable in water. In addition, they pass readily through the gills
    of fish, compared with chlorine, which does not easily enter the bloodstream. When a
    water conditioner is added to water containing chloramines, the chloramine is destroyed,
    but what is left is ammonia, also toxic to fish. In addition, some water companies tend to
    add an excess of ammonia to the water when producing chloramines, which means that
    some ammonia may already be present before you use a water conditioner to destroy the
    Fish affected with chloramine poisoning will show abnormal swimming behaviour. They
    tend to remain motionless or rock in a side-to-side motion. Some fish will also rest on the
    bottom of the aquarium and cease feeding. Death from chloramine or chlorine toxicity is
    To avoid poisoning by either chlorine or chloramine, always use a water conditioner to

        prepare the water for use. Whenever you make water changes, you must also treat the
        water to destroy these toxins. If you suspect chloramines are added to your water, you
        should call your municipal water company and ask if they are using the chloramination
        process. If they are, you will need to ensure that all water is treated to destroy the
        chloramines and to reduce the concentration of ammonia. You can reduce ammonia
        concentrations by either using activated carbon or specific ammonia-removing chemicals
        that are available commercially. It is also recommended that you acquire a total chlorine
        test kit for measuring chlorine and chloramines.
       Heavy Metals: Copper, lead, aluminium and others are very toxic to fish. Copper
        medications are useful for controlling various disease agents when used at specific
        concentrations; however, in high concentrations, copper is capable of killing fish.
        Invertebrates         cannot         be        exposed       to        any        copper.
        Heavy metals can be introduced to the aquarium by the use of contaminated water, the
        introduction of decorative items that contain heavy metals, or the addition of chemicals.
        Municipal water supplies can also be a source of copper (some municipalities add copper
        to their reservoirs to control the growth of algae). Copper and other metals can also be
        introduced when water is passed through metal piping or stored in galvanised buckets.
        Copper poisoning through overdosage can occur when copper medications are added to
        the aquarium for treatment, but the water is not properly monitored with a copper test kit.
        Fish affected by heavy metal poisoning generally show similar signs of poisoning with
        other toxins in the water. The fish will become lethargic, develop increased respiration,
        cease eating, and die rapidly.
        In order to prevent metal poisoning of aquarium fish, always use water conditioners that
        contain special chemicals to render heavy metals non-toxic. In addition, never store water
        in metal containers, and check with your water company to see if they ever add metal
        compounds to the water to control algae in reservoirs. If you suspect you live in a building
        with copper piping, use a copper test kit to check the water prior to using it in an
       Pesticides: Commonly used for eradicating insects, these are often very toxic to fish. It is
        important to protect the aquarium from accidental poisoning by these products. If you
        must use sprays, be sure to cover the aquarium and temporarily disconnect the air pump
        to prevent the insecticide from being pumped into the water. Depending on the size of the
        aquarium and number of fish, the filtration and air pumps should not be disconnected for
        several hours. Before starting again, make sure the room is well ventilated to remove any
        residual airborne insecticides.
        Fish affected with pesticides will demonstrate a variety of signs of toxicity. They will gasp
        at the water surface, lose their normal colour, and swim abnormally. As with other water
        toxicity, all the fish will be affected. If you suspect that the water has been contaminated
        with a pesticide, you must make a major water change to reduce the toxin. In addition,
        change the activated carbon in the filter and continue normal filtration. Activated carbon is
        capable of rapidly removing many pesticides from water.


Deficiencies in nutrients can induce disease. The majority of diet-related problems can easily be
averted by providing a variety of foods.

Diseases related to deficiencies, including inadequate protein and vitamins, appear to be the
major problem with aquarium fish. On the other hand, feeding inappropriate food or excessive

amounts of food can also be detrimental. Fatty degeneration of the liver occurs when fish have
too much fat in their diet.

Starvation is one of the most serious problems of aquarium fish. A refusal of fish to feed for more
than several days can be related to infectious disease, aggression by tank-mates, or disinterest in
the type of food offered. Some species of fish are specialised in their feeding requirements; it is
not uncommon for them to refuse various foods. Make sure you know what the fish have been
eating before you purchase them.

It is not unusual for a fish to refuse to eat for several days after introduction to a new aquarium.
This should be considered normal. Generally, within a few days fish will begin eating properly. If
the fish continue to refuse to feed, make sure that this is not related to aggression from other
tankmates. If this is not the cause, offer some other types of food, including live foods. In the
majority of cases, this will solve the problem.

Nutrition is a critical factor in the longevity of decorative fish in aquariums. Since the greater
majority of fish are caught in the wild, the aquarist faces the problem of providing foods that are
good substitutes for those normally eaten in the natural habitat. The diet must include enough
variety to supply the appropriate proportion of nutrients.

Satisfying the requirements of freshwater fish can be sometimes problematic. Many species have
strict requirements for only certain types of foods. For example, some species will eat only live
foods. There are species of fish that are so specific in their feeding habits that they should never
be purchased for a home aquarium. Though the study of freshwater fish nutrition is in its infancy,
research to date has provided information on their generalised requirements.
The health and longevity of aquarium fish largely depend on the quality and quantity of the diet.
The nutritional needs of fish are not static, but change especially during demanding physiological
periods. To ensure normal growth, structural tissue and organ integrity, reproduction,
physiological function, and disease resistance, fish must have nutritionally sound diets.
To minimise deficiencies under aquarium conditions, freshwater fish diets must be varied; the diet
can include frozen foods, live foods, and prepared dry foods. Each of these types will be
examined later.

Food furnishes usable energy for growth, tissue repair, swimming, and other essential activities.
The rate at which energy is used, called the metabolic rate, is a function of various factors,
including temperature, the species of fish, its body size, and its physical condition.
You must understand that water temperature is the most important factor affecting a fish's
metabolic rate. This is due to the fact that a fish's body temperature is always close to the
ambient water temperature. Therefore, if the aquarium water is 80 F (26.6°C), the fish's body
temperature will also be close to 80°F (26.6°C). As the water temperature increases, so does the
metabolism of the fish and its energy requirements.

Aquarium fish also have variable energy requirements depending on the species. In order to
maximise growth, young fish require more calories than older fish.

       Feeding Behaviour of Fish
       Dietary Requirements
       Types of Foods
       Guidelines for Feeding Fish

Feeding Behaviour of Fish

Fish species are classified as herbivores, carnivores, or omnivores. This is a generalisation, since
food habits can change depending on the species, the size of the fish, and the stage of its life.
Herbivores feed on plant materials almost exclusively. Fish such as various surgeonfish and
parrotfish are classified as herbivorous. They consume large quantities of algae and other plant
materials each day. Research has shown that plant materials can account for 94 percent or more
of their daily diet. Such animals have evolved a long intestinal tract that allows for the longer time
required to digest plant materials.

Carnivores prey either on other fishes, invertebrates, or both. In contrast to herbivorous fishes,
carnivores       have       evolved      a      shorter   intestine    for     digesting     food.
Omnivores feed on a variety of both plant and animal materials. The great majority of fishes are
classified as omnivorous. As can be expected, omnivores have developed an intestinal tract
suited for the digestion of a wide variety of foodstuffs.

Dietary Requirements

The basic nutrients required by fish include proteins, lipids, carbohydrates, vitamins, and
minerals. Although the exact requirements of each species are unknown, research on freshwater
fish has provided basic guidelines for feeding aquarium fish.


Aquarium fish have a requirement for abundant protein in their diet. In nature, protein comprises
the largest portion of the diet. Young fish require higher protein levels than adults. If a fish diet is
lower in protein than required, growth rates, tissue repair, and disease resistance are directly
Proteins are found in plant and animal materials and are comprised of amino acids. The
nutritional value of a particular protein is based on the types and amounts of its amino acids.
Animal proteins are more complete, providing essential amino acids often absent in plant
proteins. There are 25 amino acids common to all proteins, of which 10 are essential to various
species of fish.

Amino acids are comprised of proteins and are divided into two categories: those that can be
synthesised by a fish by chemically converting one amino acid to another, and those that must be
supplied    in    the   diet.  The     latter     type  is   called   essential  amino    acids.
With the exception of a few species, very little is known about the exact minimum requirement of
amino acids needed by fish. From research thus far, it is recommended that fish receive a
minimum of 40 to 55 percent protein (dry weight basis) in their diet, depending on the species.
Herbivorous fishes have a lower protein requirement while carnivores and omnivores have a
higher protein requirement.


Lipids or fish oils are a critical portion of the diet. These nutrients are used as energy sources and
are required for the synthesis of various components of the fish's body.
The active components of dietary lipids are called fatty acids, which are comprised of long chains
of carbon atoms. They can be either saturated or unsaturated, depending on the chemical
structure of the lipid. Fish oils are mostly unsaturated; the fats of higher vertebrates are saturated.
As with proteins, there are essential unsaturated fatty acids required by fish. Fish are able to
synthesise some fatty acids from other fats, but certain fatty acids must be received in the diet.
Aquarium fish need long-chained fatty acids, often found in other aquatic organisms.
Too much fat in the diet of aquarium fish can cause accumulations of fat in the internal organs.
Abnormal fat deposits in organs such as the kidneys and liver can interfere with the normal
structure and function of these organs. Fish with such conditions tend to be prone to disease.


This nutrient group consists of sugars and starches. Carbohydrates are utilised by being
chemically converted to sugars and then absorbed as an energy source, or being stored in the
tissues for later use. Carbohydrates are important because they are essential for the conversion
of amino acids and fats into various other components required for normal functioning.

While carbohydrates are an important part of the diet, not all fish can utilise carbohydrates
In contrast to various species of freshwater fish that are efficient users of carbohydrates, fish
cannot as readily utilise carbohydrates in the diet. Therefore, for the majority of species
maintained in the aquarium, carbohydrates should not constitute a large part of the diet.
Herbivorous fishes, such as many species of parrotfishes and surgeonfishes, however, are more
efficient users of carbohydrates.

An excess of carbohydrates in the diet of fish is known to cause liver degeneration and
associated diet-related diseases.


Vitamins are required in the diets of all fish. They have a different function from that of proteins,
fats, and carbohydrates, as they are not a source of energy. Vitamins act as catalysts for other
chemical reactions in the fish's body.

Vitamins are a large group and are either water-soluble or fat-soluble. The water-soluble vitamins
include the B-complex group, such as riboflavin, thiamine, and pyridoxine, as well as vitamin C.
Water-soluble vitamins are abundantly found in various foods, including yeast, leafy plants, algae,
and cereals. The fat-soluble types are vitamins A, E, D, and K. Fat-soluble vitamins are found in
various fats and oils.

Some problems can occur with the leaching of vitamins into the water from dry or prepared foods.
It is known that within a few seconds after feeding, some water-soluble vitamins can be reduced
substantially. On the other hand, vitamins are easily lost as a result of heat exposure or the
presence of other chemical compounds that reduce vitamin activity. However, recent discoveries
have partially solved the problem of vitamin depletion in prepared foods.
A fish that is fed a vitamin deficient diet will utilise the stored vitamins in its body, eventually
exhausting its available vitamin reserve. If the depletion continues, deficiency signs will develop.
Notable signs of vitamin deficiencies include weight loss, slow growth, loss of pigmentation,
blindness, and increased predisposition to infection.


Fish are capable of absorbing some minerals directly from their environment. In addition, since
aquarium fish continually swallow small amounts of water, they are ingesting minerals beyond
their minimum requirements for normal bodily functions, including haemoglobin production and
bone formation. Mineral deficiency is extremely rare in fishes.

Iodine deficiency is the most common mineral deficiency in fish diets. Calcium and phosphorous
are required for normal growth. Lack of these, moreover, may cause spinal curvature and
deformed skulls in fish.

Diets that have adequate fish protein are good sources of minerals.

Types of Foods

Various types of foods are available for aquarium fish. A good diet will include the requirements of
each species. For this discussion, the types of foods are divided into live foods, fresh and frozen
foods, and prepared dry foods.

Live Foods

Several live foods are readily available, such as tubifex worms and artemia. The advantage of
feeding live foods is that the animal is receiving the ideal undeteriorated natural food,
unadulterated by preservatives. Certain species of fish will eat only live foods. The disadvantage
of some live foods is that they can be carriers of disease agents.

Tubifex Worms: These are also readily available for feeding aquarium fish. These worms have
high nutritional value and are readily accepted by fish. They can be maintained alive for several
days or longer, depending on storage conditions.

The disadvantage of these worms is that they must be consumed immediately, before they
burrow into the substrate, where they could foul the aquarium water. Start with a small portion of
worms, adding worms only after the previous portion has been eaten.

Water flea (Cladocera) lives mainly in standstill water, such as lakes and marshes. They
measure between 1 and 6 mm. Water flea moves in the water by jumping. This kind of food has
many advantages. For example, the uneaten ones do not moulder and thus pollute the water in
the aquarium.

White Worms (Enchytraeus): These small worms are a good food supplement for small fish.
White worms are available commercially, but they are often bred at home by aquarium hobbyists.
However, as with the culture of any live food, it requires time and patience for best results.
White worms must be rinsed well prior to feeding to aquarium fish. As with tubifex worms, only
small numbers should be fed to ensure that the worms are consumed within a reasonable time.
While white worms are an excellent food, they should be considered only a supplement for fish.
Enhitreus (Enchytraeus) is about 1-1.5 cm long. It is very healthful food because fish does not
get fat and this is very important for the reproduction. But this does not mean you should use
them all the time. Remember that changing the food is vital for the proper fish growth.
Brine shrimp (Artemia salina) is very valuable food and for decorative fish. It's also very suitable

for feeding newly born fish. Some aquarists advice that it is better to have snails in your aquarium
so that they can eat the death artemia larvae.

Fresh and Frozen Foods

More convenient and more readily available than many live foods, various fresh and frozen foods
are suitable major staples of the fish diet. Fresh foods such as fish fillets, shrimp, clams, and
scallops are all excellent choices for feeding young aquarium animals. Various plant materials,
including spinach, lettuce, and algae, are good supplements in diets of herbivorous and
omnivorous fishes.

Fish: Fresh fish is an excellent component of the diet for aquarium fish. An ample supply of fish
can be purchased, cut into smaller pieces, and frozen for later use. If prepared properly, you can
then remove a portion from the freezer, thaw the food in a small amount of warm water, and feed
to the aquarium inhabitants.

Shrimp: Fresh raw shrimp is one of the best staple foods for feeding aquarium fish. It can be
used for feeding small fish by cutting the shrimp into small pieces. Large chunks of shrimp will be
readily taken whole by larger fish. Pieces of shrimp are also excellent for feeding sea anemones,
hermit crabs, and other invertebrates.

Plant materials: Spinach, lettuce, algae, and other plant materials can also be fed either fresh or
frozen. If fresh materials are used, they should be briefly steamed just enough to wilt the plants.
This makes it easier for fish to consume lettuce or spinach. Frozen spinach can be used after it is
thawed. Plant materials are essential dietary items for herbivorous fishes such as surgeonfishes
and parrotfishes.

Prepared Dry and Freeze-Dried Foods

This group of aquarium foods is either prepared from various ingredients and then processed into
flakes or pellets, or freeze-dried. The freeze-dried natural foods are daphnia, tubifex worms, etc.

Flake Foods: The most popular prepared foods for aquarium fish, high-quality flake foods are
excellent for freshwater fish, but should not be relied on as a sole diet for fish.
Flake foods are prepared from a complex group of ingredients that are blended into a slurry and
then pumped to a specialised drum dryer. As the slurry comes into contact with the dryer, the
food is rapidly baked. Large wafer-thin sheets are produced, which are then broken into flakes.
To prevent overfeeding, flake foods should be fed sparingly, a small amount at a time.

Pellet Foods: These foods are available in two types - sinking pellets and floating pellets.
The sinking pellet is a highly compressed globule of a granular food formula that has been
steamed and forced through a die. This type of pellet sinks to the aquarium bottom and rapidly
hydrates and swells.

Floating pellets are manufactured using high levels of pressure, heat, and moisture. In the
process, the large amounts of carbohydrates used in extrusion formulas become gelatinised,
trapping air within the pellet. However, floating foods are generally not recommended. Floating
foods are useless for feeding.

Guidelines for Feeding Fish

Proper technique for feeding must take into consideration the natural feeding habits of the fish. It
is often recommended that aquarium fish be fed either once or twice a day. Contemporary
thought on feeding aquarium fish takes into consideration the feeding behaviours in the natural
habitat of the fish; therefore, the recommendation is to offer multiple small feedings throughout
the day. It is also important to understand that for proper growth, young fish must receive more
food than older fish.

How to Feed

The most serious problems are overfeeding and underfeeding. The former is far more common
than the latter. The most serious consequence of overfeeding is the accumulation of uneaten
food that can decay foul the water through the build-up of ammonia, and possibly result in the
death of the fish.

Underfeeding is a problem either when fish are fed too little or when dominant fish in the
aquarium consume the greatest amount of food. In this situation, some fish receive ample
nutrition, while others are nutritionally deprived. The feeding behaviour of the fish in the aquarium
must therefore be considered.

Depending on the species, each type of fish has a different behaviour. There are surface feeding
fish, mid-water feeders, and bottom-feeding fishes. When feeding the inhabitants of a community
aquarium, ensure that each species is receiving a share of the food.
As a general rule, your aquarium fish should be fed two to four times daily. The feeding periods
should be distributed throughout the day. Young fish may require more frequent feedings.
Alternate the types of food fed each day. Include in the diet various types, such as flake foods,
freeze-dried foods, and frozen foods. Always offer small amounts of food at each feeding period,
adding any additional food only after the first portion has been completely consumed.
At the conclusion of the feeding period, always remove any food that remains uneaten on the
bottom to prevent decay that can pollute the aquarium water. This is especially important when
feeding frozen and fresh foods such as clams, mussels, and shrimp, which can rapidly pollute the

Problem Fish

It is inevitable that some fish will be reluctant to feed, especially if they have been recently
introduced to the aquarium. If they do not eat for several days, it is generally not serious;
however, if the problem persists, it could be related to other difficulties, including disease. On the
other hand, if the animal appears otherwise normal, its apparent lack of appetite may simply be
related to the type of food offered. In that case, you should try a different type of food.
Other causes for not eating could be aggression by other aquarium fish, or simply that the fish is
a shy species that normally does not feed in the open when aggressive fish are eating.
You should also keep in mind that if prepared dry foods are offered, it takes time for fish to
become acclimated to this type of food. This is especially true if the fish have been fed mostly live
or frozen foods in the pet shop. It is always best to ask the retailer what types of food were used.

All fish reproduce sexually. In sexual reproduction, a sperm unites with an egg in a process called
fertilisation. The fertilised egg develops into a new individual. In almost all fish species, males
produce sperm and females produce eggs. In a few species, the same individual produces both
sperm and eggs.

The eggs of most fish are fertilised outside the female's body. A female releases her eggs into the
water at the same time that a male releases his sperm. Some sperm come in contact with some
of the eggs, and fertilisation takes place. This process is called external fertilisation. The entire
process during which eggs and sperm are released into the water and the eggs are fertilised is
called spawning. Almost all bony fish reproduce in this way.

Sharks, rays, chimaeras, and a few bony fish, such as guppies and mosquito fish, reproduce in a
different manner. The eggs of these fish are fertilised inside the female, a process called internal
fertilisation. For internal fertilisation to occur, males and females must mate. The males have
special organs for transferring sperm into the females. After fertilisation, the females of some
species release their eggs into the water before they hatch. Other females hatch the eggs inside
their bodies and so give birth to living young. Fish that bear living young include many sharks and
rays, guppies, and some halfbeaks and scorpionfish.

Preparation for spawning

Most fish have a spawning season each year, during which they may spawn several times. But
some tropical species breed throughout the year. The majority of fish spawn in spring or early
summer, when the water is warm and the days are long. But certain cold-water fish, such as
brook trout and Atlantic cod, spawn in fall or winter.

Most fish return to particular spawning grounds year after year. Many freshwater fish have to
travel only a short distance to their spawning grounds. They may simply move from the deeper
parts of a river or lake to shallow waters near shore. But other fish may migrate tremendous
distances to spawn.

At their spawning grounds, the males and females of some species swim off in pairs to spawn.
Among other species, the males and females spawn in groups. Many males and females tell
each other apart by differences in appearance. The females of some species are larger than the
males. Among other species, the males develop unusually bright colours during the spawning
season. During the rest of the year, they look much like the females of their species. In some
species, the males and females look so different that for many years scientists thought they
belonged to different species. Among other fish, the sexes look so much alike that they can be
told apart only by differences in their behaviour. For example, many males adopt a special type of
courting behaviour to attract females. A courting male may swim round and round a female or
perform a lively "dance" to attract her attention.

Among some species, including cod, Siamese fighting fish, and certain gobies and sticklebacks, a
male claims a territory for spawning and fights off any male intruders. Many fish, especially those
that live in fresh water, build nests for their eggs. A male freshwater bass, for example, uses its
tail fin to scoop out a nest on the bottom of a lake or stream.

Spawning and care of the eggs

After the preparations have been made the males and females touch in a certain way or make
certain signals with their fins or body. Depending on the species, a female may lay a few eggs or
many eggs - even millions - during the spawning season. Most fish eggs measure 1/8 inch (3
millimetres) in diameter or less.

Some fish, such as cod and herring, abandon their eggs after spawning. A female cod may lay as
many as 9 million eggs during a spawning season. Cod eggs, like those of many other ocean fish,
float near the surface and scatter as soon as they are laid. Predators eat many of the eggs.
Others drift into waters too cold for hatching. Only a few cod eggs out of millions develop into
Adult fish. A female herring lays about 50,000 eggs in a season. But herring eggs, like those of
certain other fish, sink to the bottom and have an adhesive covering that helps them stick there.
As a result, herring eggs are less likely to be eaten by predators or to drift into waters
unfavourable for hatching.

A number of fish protect their eggs. They include many freshwater nest builders, such as bass,
salmon, certain sticklebacks, and trout. The females of these species lay far fewer eggs than do
the females of the cod and herring groups. Like herring eggs, the eggs of many of the freshwater
nest builders sink to the bottom and have an adhesive covering. But they have an even better
chance of surviving than herring eggs because they receive some protection.
The amount and kind of protection given by fish to their eggs vary greatly. Salmon and trout cover
their fertilised eggs with gravel but abandon them soon after. Male freshwater bass guard the
eggs fiercely until they hatch. Among ocean fish, female seahorses and pipefish lay their eggs in
a pouch on the underside of the male. The eggs hatch inside the male's pouch. Some fish,
including certain ocean catfish and cardinal fish, carry their eggs in their mouth during the
hatching period. In some species, the male carries the eggs. In other species, the female carries

Hatching and care of the young

The eggs of most fish species hatch in less than two months. Eggs laid in warm water hatch
faster than those laid in cold water. The eggs of some tropical fish hatch in less than 24 hours. On
the other hand, the eggs of certain cold-water fish require four or five months to hatch. The males
of a few species guard their young for a short time after they hatch. These fish include freshwater
bass, bowfins, brown bullheads, Siamese fighting fish, and some sticklebacks. But most other fish
provide no protection for their offspring.


Ethology studies behaviour of animals and fish in any certain situation. Every species has its own
"composition" of behaviour reactions; some conduct elements are inborn while others - artificial.
Behaviour is natural result or reaction towards a certain incitement. The key impulses are usually
accompanied with changes in colors or movements of fishes. Each kind has a unique behaviour
when, for example, chasing their prey or eating it, and all of these actions are genetically
determined. Fish protects itself by camouflage, flight, and even "weapons" - sharp prickles,
poisonous glands, etc. Between each other fishes may be friendly or inimically disposed, while in
other cases they do not pay attention to one another. When fish are in room their behaviour is
characterised as "yawning" or sleep.

The relations between fish from one species are very interesting. Most fishes constantly live in
flocks where they are related and dependant on each other. In the flock a fish can be aggressive,
timid, attractive, courting, etc. In other words it can be said that fishes behaviour is very
complicated and multiformal.

To describe the term "behaviour" in general some others should be introduced.
Fight During their whole life fishes fight for various things, especially in the reproduction period.
Fighting individuals usually belong to one and the same sex. Fish seldom fight for food but more
often - for living site, shelter, female specimens, for their offspring, etc. The martial bahaviour
differentiates some certain stages:

       Threatening that is expressed in taking a frontal or cross position. Fish spread their fins
        and open their gills.
       Swimming around in a narrow circle. The head of one of fishes is near the other ones' tai
        and vice versa. They make attempts to bite and hit one another.
       Threatening by tail hits.
       Mutual biting and pressing their bodies.
       The waeker individual runs away and takes sobordinate subjugated position. It's
        interesting to notice that this changes fishes' coloration.

Teritory Each fish has its area. Male individuals are able to defend their teritory for hours and
even days. The purpose of area in nature is to disrtribute population uniformly in the inhabited

Spawn Spawn of eggs is followed by their fertilization. The true spawn is preceded by various
long-standing preparations, "overture" and sometimes "wedding dances". The aims of these
actions are mutual attraction, aqiaitance and synchronizing of both partners.

Cares for progeny Some kinds look after their progeny. It can be expressed in different means.
Fishes may bring up little ones on flat stones or plant leaves, in anest or small caves, and even
"incubate" spawn in their mouths.

Behaviour of fish and animals in the wild very much differs from the one in the home aquarium. It
is not possible all aspects of their reactions to be described. Unsufficient space, disability to
choose an appropriate partner, etc., have a cosiderable effect over fish's behaviour. At that point
almost everything depends on aquarists' ability to "understand" fish. Demeanour of fishes is not
constant and a lot of patience is necessary.


Getting Food

Most fish are carnivores (meat-eaters). They eat shellfish, worms, and other kinds of water
animals. Above all, they eat other fish. They some-times eat their own young. Some fish are
mainly herbiwes (plant-eaters). They chiefly eat algae and other water plants. But most plant
eating fish probably also eat animals. Some fish live mainly on plankton. They include many kinds
of flying fish and herring and the three largest fish of all - the whale shark, giant manta ray, and
basking shark. Some fish are scavengers. They feed mainly on waste products and on the dead
bodies of animals that sink to the bottom.

Many fish have body organs specially adapted for capturing food. Certain fish of the ocean
depths attract their prey with flashing lures. The dorsal fin of some anglerfish dangles above their
mouth and serves as a bait for other fish. Such species as gars and swordfish have long, beaklike
jaws, which they use for spearing or slashing their prey. Barracudas and certain piranhas and
sharks are well known for their razor-sharp teeth, with which they tear the flesh from their victims.
Electric eels and some other fish with electricity-producing organs stun their prey with an electric
shock. Many fish have comblike gill rakers. These structures strain plankton from the water
pumped through the gills.

Most fish gain thrust (power for for-ward movement) by swinging the tail fin from side to side while
curving the rest of the body alternately to the left and to the right. Some fish, such as marlin and
tuna, depend mainly on tail motion for thrust. Other fish, including many kinds of eels, rely chiefly
on the curving motion of the body. Fish manoeuvre by moving their fins. To make a left turn, for
example, a fish extends its left pectoral fin. To stop, a fish extends both of its pectoral fins.
A fish's swimming ability is affected by the shape and location of its fins. Most fast, powerful
swimmers, such as swordfish and tuna, have a deeply forked or crescent-shaped tail fin and
sickle-shaped pectorals. All their fins are relatively large. At the other extreme, most slow
swimmers, such as bowfins and bullheads, have a squared or rounded tail fin and rounded

All fish, except the largest ones, live in constant danger of being attacked and eaten by other fish
or other animals. To survive, fish must be able to defend themselves against predators. If a
species loses more individuals each generation than it gains, it will in time die out.

Protective coloration and protective resemblance are the most common methods of self-defence.
A fish that blends with its surroundings is more likely to escape from its enemies than one whose
colour or shape is extremely noticeable. Many fish that do not blend with their surroundings
depend on swimming speed or manoeuvring ability to escape from their enemies.
Fish also have other kinds of defence. Some fish, such as gars, pipefish, and seahorses, are
protected by a covering of thick, heavy scales or bony plates. Other species have sharp spines
that are difficult for predators to swallow. In many of these species, including scorpion fish, sting
rays, and stonefish, one or more of the spines are poisonous. When threatened, the porcupine
fish inflates its spine-covered body with air or water until it is shaped like a balloon. The fish's
larger size and erect spines may discourage an enemy. Many eels that live on the bottom dig
holes in which they hide from their enemies. Razor fish dive into sand on the bottom. A few fish
do the opposite. For example, flying fish and needlefish escape danger by propelling themselves
out of the water.

Like all animals, fish need rest. Many species have periods of what might be called sleep. Others
simply remain inactive for short periods. But even at rest, many fish continue to move their fins to
keep their position in the water.

Fish have no eyelids, and so they cannot close their eyes when sleeping. But while asleep, a fish
is probably unaware of the impressions received by its eyes. Some fish sleep on the bottom,
resting on their belly or side. Other species sleep in midwater, in a horizontal position. The
slippery dick, a coral-reef fish, sleeps on the bottom under a covering of sand. The striped
parrotfish, another coral-reef fish, encloses itself in an "envelope" of mucus before going to sleep.
The fish secretes the mucus from special glands in its gill chambers.

Certain air-breathing fish, such as the African and South American lungfish, sleep out of water for
months at a time. These fish live in rivers or ponds that dry up during periods of drought. The fish
lie buried in hardened mud until the return of the rainy season. This kind of long sleep during dry
periods is called estivation. During estivation, a fish breathes little and lives off the protein and fat
stored in its body.

Living Together

Among many species, the individual fish that make up the species live mainly by themselves.
Such fish include most predatory fish. Many sharks, for example, hunt and feed by themselves
and join other sharks only for mating.

Among many other species, the fish live together in closely-knit groups called schools. About a
fifth of all fish species are schooling species. A school may have few or many fish. A school of
tuna, for example, may consist of fewer than 25 individuals. Many schools of herring number in
the hundreds of millions. All the fish in a school are about the same size. Baby fish and adult fish
are never in the same school. In some schooling species, the fish become part of a school when
they are young and remain with it throughout their lives. Other species form schools for only a few
weeks after they hatch. The fish in a school usually travel in close formation as a defence against
predators. But a school often breaks up at night to feed and then regroups the next morning. The
approach of a predator brings the fish quickly back together.

Fish also form other types of relationships. Among cod, perch, and many other species, a number
of individuals may gather in the same area for feeding, rest or spawning. Such a group is only

temporary and is so closely knit as a school. Some fish, including certain angelfish and wrasses,
form unusual relationships with larger fish of other species. In many such relationships the
smaller fish removes parasites or dead tissue from the larger fish. The smaller fish thus obtains
food, and the other is cleaned.

Adjusting to Changes

Fish sometimes need to adjust to changes in their environment. The two most common changes
are (1) changes in water temperature and (2) changes in the salt content of water.
In general, the body temperature of each species fish equals that of the water in which the
species live the water temperature rises or falls, a fish can adjust to the change because its body
temperature changes accordingly. But the change in the water temperature has not to be too
great and must occur gradually. Most fish can adjust to a change in the water temperature of up
to 15°F. (8° C) - if the change is not sudden. Water temperatures usually change slowly, and so
there is time for fish's body to make the necessary adjustment. But occasionally, the temperature
drops suddenly and severely killing many fish. In addition, freshwater fish are some-times
endangered by thermal pollution, which occurs when factories and electric power plants release
hot water into rivers or lakes. The resulting increase in water temperature may be greater than
most fish can adjust to.

Both fresh water and ocean water contain various salts, many of which fish need in their diet. But
ocean water is far saltier than fresh water. Fish that migrate between the two must adjust to
changes in the salt c< of the water. Relatively few fish can make such an adjustment.
Both freshwater and saltwater fish have about the same amount of dissolved salts in their body
fluid! The body fluids of ocean fish are not so salty as the in which the fish live. Under certain
circumstances water from a weak solution will flow into a strong solution. This natural process,
called osmosis, takes place when the two solutions are separated by a membrane (tissue layer)
through which only the water can pass. The skin and gill membranes of fish are of one type. For
this reason, fish constantly lose weight from their body fluids into the stronger salt solutions in the
seawater. To make up for this loss, they drink water. But ocean water contains more salt than
many fish need. The fish pass the extra salt out through gills and through their digestive tract.
Saltwater fish need all the water they drink. As a result, these fish reduce only small amounts of
Freshwater fish have the opposite problem with osmosis. Their body fluids are saltier than fresh
water and as a result, the fish constantly absorb water through their membranes. In fact,
freshwater fish absorb so much water that they do not need to drink any. Instead fish must get rid
of the extra water that their bod sorb. As a result, freshwater fish produce great quantities of


Like all vertebrates, fish have sense organs that tell them what is happening in their environment.
The organs enable them to see, hear, smell, taste, and touch. In addition, almost all fish have a
special sense organ called the lateral line system, which enables them to "touch" objects at a
distance. Fish also have various other senses that help them meet the conditions of life


A fish's eyes differ from those of land vertebrates in several ways. For example, most fish can
see to the right and to the left at the same time. This ability makes up in part for the fact that a fish
has no neck and so cannot turn its head. Fish also lack eyelids. In land vertebrates, eyelids help
moisten the eyes and shield them from sunlight. A fish's eyes are kept moist by the flow of water
over them. They do not need to be shielded from sunlight because sunlight is seldom extremely
bright underwater. Some fish have unusual adaptations of the eye. For example, adult flatfish
have both eyes on the same side of the head. A flatfish spends most of the time lying on its side
on the ocean floor and so needs eyes only on the side that faces up-ward. The eyes of certain
deep-sea fish are on the ends of short structures that stick out from the head. These structures
can be raised upward, allowing the fish to see overhead as well as to the sides and front.
A few kinds of fish are born blind. They include certain species of catfish that live in total darkness
in the waters of caves and the whalefish, which lives in the ocean depths. Some of these fish
have eyes but no vision. Others lack eyes completely.


All fish can probably hear sounds produced in the water. Fish can also hear sounds made on
shore or above the water if they are loud enough. Catfish and certain other fish have a keen
sense                                            of                                  hearing.
Fish have an inner ear enclosed in a chamber on each side of the head. Each ear consists of a
group of pouches and tubelike canals. Fish have no outer ears or eardrums to receive sound
vibrations. Sound vibrations are carried to the inner ears by the body tissues.

Smell and taste

All fish have a sense of smell. It is highly developed in many species, including catfish, salmon,
and sharks. In most fish, the olfactory organs (organs of smell) consist of two pouches, one on
each side of the snout. The pouches are lined with nerve tissue that is highly sensitive to odours
from substances in the water. A nostril at the front of each pouch allows water to enter the pouch
and pass over the tissue. The water leaves the pouch through a nostril at the back.
Most fish have taste buds in various parts of the mouth. Some species also have them on other
parts of the body. Catfish, sturgeon, and a number of other fish have whiskerlike feelers called
barbels near the mouth. They use the barbels both to taste and to touch.
Touch and the lateral line system are closely related. Most fish have a well-developed sense of
touch. Nerve endings throughout the skin react to the slightest pressure and change of
temperature. The lateral line system senses changes in the movement of water. It consists mainly
of a series of tiny canals under the skin. A main canal runs along each side of the trunk. Branches
of these two canals extend onto the head. A fish senses the flow of water around it as a series of
vibrations. The vibrations enter the lateral line through pores and activate certain sensitive areas
in the line. If the flow of water around a fish changes, the pattern of vibrations sensed through the
lateral line also changes. Nerves relay this information to the brain. Changes in the pattern of

vibrations may warn a fish of approaching danger or indicate the location of objects outside its
range of vision.

Touch and the Lateral Line System

Touch and the lateral line system are closely related. Most fish have a well-developed sense of
touch. Nerve endings throughout the skin react to the slightest pressure and change of
temperature. The lateral line system senses changes in the movement of water. It consists mainly
of a series of tiny canals under the skin. A main canal runs along each side of the trunk. Branches
of these two canals extend onto the head. A fish senses the flow of water around it as a series of
vibrations. The vibrations enter the lateral line through pores and activate certain sensitive areas
in the line. If the flow of water around a fish changes, the pattern of vibrations sensed through the
lateral line also changes. Nerves relay this information to the brain. Changes in the pattern of
vibrations may warn a fish of approaching danger or indicate the location of objects outside its
range                                              of                                          vision.
Other senses include those that help a fish keep its balance and avoid unfavourable waters. The
inner ears help a fish keep its balance. They contain a fluid and several hard, free-moving otoliths
(ear stones). Whenever a fish begins to swim in other than an upright, level position, the fluid and
otoliths move over sensitive nerve endings in the ears. The nerves signal the brain about the
changes in the position of the body. The brain then sends messages to the fin muscles, which
move to re-store the fish's balance. Fish can also sense any changes in the pressure, salt
content, or temperature of the water and so avoid swimming very far into unfavourable waters.

Other Senses

Other senses include those that help a fish keep its balance and avoid unfavourable waters. The
inner ears help a fish keep its balance. They contain a fluid and several hard, free-moving otoliths
(ear stones). Whenever a fish begins to swim in other than an upright, level position, the fluid and
otoliths move over sensitive nerve endings in the ears. The nerves signal the brain about the
changes in the position of the body. The brain then sends messages to the fin muscles, which
move to re-store the fish's balance. Fish can also sense any changes in the pressure, salt
content, or temperature of the water and so avoid swimming very far into unfavourable waters.


Carnivores are meat-eating fish. Some prefer live prey that they can hunt down
and kill before eating, such as other fish or insects. Here are some common
carnivorous fish, and what they prefer to eat.

                 Acara - Accepts all types of meaty foods.
                 Apistogramma - Apistos prefer live foods, but will eat
                  beefheart and even pellets.
                 Archerfish - Eats live foods exclusively.
                 Banjo Catfish - Prefers live foods, but can be trained to accept
                  freeze dried tablets.
                 Bettas - Prefers live foods but will accept flakes and freeze
                 Electric Catfish - Prefer live foods, but can be trained to
                  accept freeze dried tablets.
                 Frontosa - Accepts all types of meaty foods.
                 Halfbeak - Prefers live foods, but will eat flakes.
                 Hatchetfish - Prefers live foods but will accept freeze dried and
                  flake foods.
                 Killifish - Eats small live foods, can be trained to accept flakes.
                 Knifefish - Eats live foods exclusively.
                 Oscar - Accepts all types of meaty foods.
                 Pencilfish - Feed small live foods.
                 Piranha - eats live foods, but can be trained to accept meat
                 Weather Loach - Live foods preferred, should be fed in the

Herbivores require a diet of all, or mostely, vegetable matter. True herbivores do
not have a large stomach, and therefore must eat more frequently. These fish are
primarily vegetarian, and should be fed accordingly.

                 Molly - Algae-eater that also eats vegetables such as spinach.
                  Will also accept insects and flakes.
                 Farowella - Eats vVegetable tablets and algae.
                 Pacu - Prefers fresh vegetables, will eat vegetable flakes and
                 Silver Dollar - Feed fresh vegetables, vegetable flakes and
                 Tropheus - Acccepts algae, plants, spirulina, vegetable flakes.

The majority of aquarium fish are omnivores, meaning they will eat both meat
and vegetables. To keep your fish healthy, fed them a varied diet that includes all
types of foods. Here are some popular omnivores, with notes about their
preferred diet.

                 Angelfish - Accepts all types of foods, but prefers live foods.
                 Armored Catfish - Accepts all types of foods, but needs lots of
                  vegetable matter. Should be fed at night just before turning off
                 Auratus - Accepts all types of foods, but prefers live food.
                 Barbs - Accepts all types of foods.
                 Blood Parrot - Accepts all types of foods.
                 Convict - Feed both meaty and vegetable based foods.
                 Corydoras - Accepts all types of foods. Bottom feeders.
                 Danios - Accepts all types of foods
                 Discus - Prefers live foods, but will accept pellet and flake
                 Festivum - Accepts all types of foods.
                 Goldfish - Accepts all types of foods, but diet should not be too
                  high in protein.
                 Gourami - Accepts all types of foods, but prefers additional
                  meat in the diet.
                 Guppy - Accepts all types of foods, prefers mosquito larvae.
                 Hap - Accepts all types of foods.
                 Jack Dempsey - Accepts flakes, pellets and live foods.
                 Julidochromis - Prefers live-food, will eat flake foods.
                 Kribensis - Accepts flakes, pellets and live foods.
                 Loaches - Most accept all types of foods, but prefer live foods.
                 Mbuna - Accepts flakes, pellets and live foods.
                 Platy - Accepts all types of foods, but needs lots of vegetable
                 Plecostomus - Accepts all types of foods, but needs lots of
                  vegetable matter. Should be fed at night just before turning off
                 Rams - Accepts flakes, pellets and live foods.
                 Severum - Accepts flakes, pellets and live foods.
                 Swordtails - Accepts all types of foods, but prefers additional
                  meat in the diet.
                 Tetras - Accepts all types of foods.
                 Zebra Danio - Accepts flakes, pellets and live foods.


The leading cause of failure with aquariums is overfeeding. Over-feeding can pollute a tank so
rapidly, that the aquarium will appear dirty a week after we’ve cleaned it. One day of over-feeding
can release more pollution into an aquarium than an entire month of normal fish waste

The next time you feed aquarium fish, drop in the amount of food that you usually feed, then
stand back and watch the fish eat from the front of the aquarium. If you see pieces of food going
to the bottom of the tank, YOU’RE OVERFEEDING! Fish are cold-blooded (poikilothermic)
animals. Their body temperature is nearly the same as the water they live in. They do not need to
keep their bodies warm the way that warm-blooded (homoeothermic) animals do, so they use a
lot less energy and therefore need less food to survive than warm-blooded (homoeothermic)

When feeding an aquarium fish, feed them only as much as they can eat in a few minutes - a little
at a time! Take a small amount of food, such as several flakes, and drop it into the tank. Then
stand away from the aquarium, and watch aquarium fish eat. When the fish have finished eating
the first portion, drop a few more pieces in, and let them finish those. After two or three portions,
you’ll notice that the fish either lose interest, or suck in the food and spit it out. Stop feeding! The
fish aren’t hungry anymore! Never throw in a "pinch" of food. A "pinch" is usually TOO MUCH.

If you have a Wet/Dry Filter, and food floating on the surface is drawn into the prefilter, try putting
the portions of food in below the water’s surface, and as far from the filter intake as possible. That
way, food will not accumulate in the prefilter.

When feeding frozen food, take a very small portion (or one cube), and allow it to partially defrost
before feeding. Feed as you would dry flake foods, breaking off small pieces of the partially
defrosted food, and waiting for your fish to eat each piece before adding more.

Don’t crush the food. Even the smallest fish have teeth, and will bite off what they need. Crushed
food will settle to the bottom faster, and pollute the water. Bottom feeders such as catfish and
loaches should be fed a sinking type food sparingly three times a week. In saltwater, Moray Eels
and other large carnivores should be fed three to five times a week.

If some of your fish are smaller or more timid about eating, don’t worry-they’ll get their share. As
the larger, more aggressive fish get full, they’ll slow down on their feeding, and the smaller fish
will "clean up" the leftovers.

Signs of overfeeding:

       Algae begins to grow back on aquarium surfaces within a week after it’s cleaned.
       Water is continually cloudy with a white appearance.
       When you test the water for ammonia, you always get a slight reading.
        (In a healthy tank, ammonia will always test at ZERO!)
       The algae that grows in the tank is slimy and black or red, instead of hair-like and green.
       Uneaten food is left at the bottom of the tank after feeding.
       Uneaten food is accumulating in the filters.
       Uneaten food accumulates in the prefilter of your Wet/Dry Filtration System.
       The aquarium sometimes has a "fishy" odor (Properly fed aquariums have no odor.)

                              Ornamental Fish Farming

        Ornamental fish keeping and its propagation has been an interesting activity for many,
which provide not only aesthetic pleasure but also financial openings. About 600 ornamental fish
species have been reported worldwide from various aquatic environments. Indian waters possess
a rich diversity of ornamental fish, with over 100 indigenous varieties, in addition to a similar
number of exotic species that are bred in captivity

Species for breeding

         Among the indigenous and exotic
freshwater species, the varieties having good
demand can be bred and reared for commercial
purpose. Species that can be produced easily
and popular as commercial varieties are coming
under egg-layers and livebearers. Among the
liver-bearer    species,    Guppies      (Peocillia
reticulata) are the simplest to start with, as the
species can tolerate great variations in water
quality and accepts all types of foods. The other
popular live bearers are Moly (Mollinesia sp.),
Sword tail (Xiphophorus sp.), and small species
like Platy.

Brood stock of rosybarbs (Puntius conchonius)

         Most important group of egg-layers comes under the family Cyprinidae, which include
carps, barbs, rasboras, danios, tetras, catfishes, etc. Goldfish (Carassius auratus) is a well-
famous aquarium fish for decades throughout the world. Koi carp (Cyprinus carpio var. koi) is
getting importance for aquariums and garden pools, in recent years with different colour
combinations. India is a land of barbs and many varieties of barbs are being suitably bred.
Indigenous danios like Zebra danio (Brachydanio rerio), tetras like Black window tetra
(Cymnocro-cymbus sp.), Neon tetra (Hyphesso-brycon innesi), Serpae tetra (Hyphessobrycon
callistus) etc. are available. A group of fish referred as bubbles-nest builders are a novelty to the
aquarium with their wonderful colours and are air-breathers. Cichlids such as angelfish,
Pterophyllum scalare are another major group for aquarium breeding. Some indigenous fishes
like Red-line torpedo fish (Puntius denisoni), Loaches (Botia sp.), leaf-fish like Nandus nandus,
snakehead (Channa orientalis) and few ornamental catfish have good demand in foreign market
and could also be tried for breeding and propagation.

          A beginner should start the work on
breeding of any live-bearer followed by goldfish
or any other egg-layer for getting acquainted
with the procedures on handling and
maintenance of brood fish and young one. Good
knowledge on the biology, feeding behavior and
ambient condition of the fish are prerequisites
for breeding. Live food like Tubifex worms,
Moina, earthworms’ etc. for brood-stock and
larval stages need special attention. The larvae
similarly need infusoria, artemia naupli, plantons
such as rotifers and smaller daphnia during the
early stage. A unit for continuous production of
 is, therefore necessary for successful maintenance                Indigenous dwarf gourami

 of the unit. In most cases breeding is easy, but larval rearing might require special care. As a
supplementary feeding the farmer can prepare on-site pelleted feed by using local agro-produce.
To avoid health related problems, a proper water quality needs to be ensured by installing
biofilters. The ornamental fishes can be bred at varied periods of the year.

Some tips for the successful production of ornamental fishes

   i)     Breeding and rearing unit should be
          made near a constant supply of water
          and electricity. If the unit is located
          near the streams, it will be excellent
          where the unit can receive portable
          water and the rearing unit can be
          made flow-through.
   ii)    Constant availability of agro-based
          byproducts like oil cakes, rice polish
          and wheat bran, and animal-based
          protein such as fish meal and prawn-
          head meal, will facilitate preparation of
          pelleted diet for the fish.
                                                             Ornamental fish culture unit of CIFA
   iii) The brood-stock selected for breeding should be of superior quality so that they produce
        quality fish for sale. It is advisable that the young ones could be grown till their maturity. It
        not only gives enough experience of handling the fish but also helps in controlled
   iv) Breeding and rearing unit may be established preferably nearer to airport/railway station
        so that live fish could be easily transported to internal market as also for export.
   v) A fish breeder could concentrate preferably on a single marketable species to streamline
        management measures.
   vi) Proper knowledge on market demand, customer preference and overall, the operation of
        a marketing network through personal contacts and public relation is desirable.
   vii) Pioneer and expert groups in this field may always be kept in touch with to keep track of
        recent developments in marketing as well as research advancements, through training.

Economics of small-scale breeding and rearing unit for live-bearers
Sl.    Item                                                                         Amount
No.                                                                               (in Rupees)
I.     Expenditure
A.     Fixed Capital
1.     Low cost shed of 300 sq. ft. area (bamboo frame with net covering)              10,000
2.     Breeding tank (6’ x 3’ x 1’6”, cemented, 4 nos)                                 10,000
3.     Rearing tank (6’ x 4’ x 2’, cemented, 2 nos)                                     5,600
4.     Brood stock tank (6’ x 4’ x 2’, cemented, 2 nos)                                 5,600
5.     Larval tank (4’ x 1’6” x 1’, cemented, 8 nos)                                    9,600
6.     Bore-well with 1 hp pump                                                         8,000
7.     Oxygen cylinder with accessories (1 no)                                          5,000
       Sub-total                                                                       53,800

B.     Variable Cost
1.     800 female, 200 male (@ Rs. 2.50/pc. of guppy, molly, swordtail & platy)         2,500
2.     Feed (150 kg/yr @ Rs. 20/kg)                                                     3,000
3.     Different types of nets                                                          1,500
4.     Electricity/fuel (@ Rs. 250/month)                                               3,000
5.     Perforated plastic breeding basket (20 nos @ Rs. 30/pc.)                           600
6.     Wages (@ Rs. 1000/month)                                                        12,000
7.     Miscellaneous expenditure                                                        2,000
       Sub-total                                                                       24,600

C.     Total Cost
1.     Variable cost                                                                   24,600
2.     Interest on fixed capital (15% per annum)                                        8,070
3.     Interest on variable cost (15% half yearly)                                      1,845
4      Depreciation (20% of fixed cost)                                                10,780
       Grand-total                                                                     45,295

II.    Gross Income
       Sale of 76800 nos. fish @ Rs. 1/pc., reared for one month (@ 40                 76,800
       nos/female/cycle from 3 cycles/year, and considering survival of 80%)

III.   Net Income (Gross income – Total cost)                                          31,505

Meet the Professional - Interview

Plamen Iliev Antonov is 54 years old and owns pet-shop 'Panda'. He is a very busy man. We had
to wait about a week to meet him and our team want to thank him that finally he found time to
answer some of our questions which we think might be interesting for you. Here they are.

Q: How does it happen so that the hobby turned into profession?

A: In general, I have studied for polygraph and have work in a publishing house for about 15
years. But after the end of the communism in Bulgaria (10.11.1989) it turned out that I do not
yearn enough money and so I had to look for a new job. That is how I started this business and
the hobby turned into a profession.

Q: According to you is the aquaristics a hobby or a way of life?
A: It could be both a hobby and a way of life but never at the same time, I know it from my
personal experience. When I started selling fish, animals, food for them and etc to do for a living
the hobby was over.

Q: Do you think that you may ever get bored of fish? Don't you think that as years are passing
fish breeding turns into a boring habit?
A: Certainly not! I do love fish and I will always love it. I can even say that I am conceived with the
fish and the sea. My ancestors have come to Varna more than two hundred years ago. I am a
passionate diver, underwater diver, fisherman, aquarist and anything else connected with water
and fish. So I can say for sure that I will never get bored of the fish. My friends even call me
Plamen "The Fish".

Q: We understood that you are the chairman of a special club called 'Club Aquaristics'
A: Yes, I am. That's true.

Q: Could you explain us what is the aim of this club?
A: This is an organisation with an ideal aim: this means it is not commercial but although its
members are people like me as well for whom this is a profession .n There are meetings each
Thursday. On these meetings lectures are given, films are watched or sometimes we just talk. But
we do much more. For example, at the moment we are collecting money from sponsors for the
Varna Aquarium which is in very bad condition, we are preparing an exhibition for the next year
and things like that. It is only the true love to fish that has gathered us all together in this club.

Q: At the end, as a conclusion, can you give some practical advice from your personal
experience to the new aquarists who have just made their first steps?
A: Oh, this is not so easy. We can talk for hours because this is a whole science. Many famous
scientists aquarists are known. They have achieved a lot but still there are many unanswered and
unstudied questions. On the other hand as a hobby the aquaristics is much more than putting a
couple of fish in an aquarium. So, my advice to the beginner-aquarist is: read and learn. This is
what a real hobby means and requires.


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