Pet Fish

There are three categories of fish suitable for the home aquarium: tropical, coldwater and marine. The marine fish require varying temperatures, from very cold to warm, depending on their natural geographical origin; because of the problems of keeping fish in saline water, they are not as popular as other fish. Tropical and coldwater fish are equally popular. It is important for those unfamiliar with the keeping of fish to read the whole of this chapter before purchasing. Fish are very sensitive and even a few hours in the wrong environment will be courting danger.

Setting up the Aquarium

Thoroughly wash the aquarium, the sand, the rocks, and the ornaments with large quantities of fresh water. Do not use soap or detergents as they are highly toxic to fish.
To wash the gravel, put it in a plastic bag or bucket and add water. Stir the gravel, then drain off the water. When the water stays clear after stirring it is free of debris and the gravel is clean. This will usually take several changes of water. The gravel can then go into the aquarium. Fill the aquarium approximately half to three-quarters full. Pour the water slowly over a plate (or into the cup of your hand) so that it does not disturb the gravel.
Connect tubing from the air pump to any outlets located inside the aquarium, such as under-gravel filters, air stones or canister filters. The canister should be loaded with filter materials and placed in the aquarium before the air line is connected. Install the air pump above the level of the water so that back-flowing water cannot destroy it, or empty the tank, if the pump fails.
Decorations and plants should now be added and arranged in such a way that the equipment is concealed or at least does not detract from the appearance of the aquarium. Live plants should be kept moist from the time you buy them till they are planted.
Add the balance of the water by pouring it slowly into your hand or a cup so that you do not disturb the gravel and plants. Fill the aquarium to near the top, leaving some air space between the water and the cover. Install the outside filter, thermostatic heater and thermometer according to manufacturers’ instructions, and plug in your air pump, power filter and heater. It will take some time for the temperature to stabilize and you may have to adjust your setting. Do not switch on the heater thermostat when it is not immersed in the water.
Water in new aquariums will often turn milky for a day or two. This is caused by a harmless bacterial growth and should disappear naturally. Check the pH and hardness of the water. After your aquarium is operating check the functioning of your equipment and the water conditions again. The temperature of the water for Goldfish should be 22°C. For tropical fish, the temperature should range between 24 and 27°C. Higher temperatures result in a higher metabolic rate in the fish; lower temperatures tend to increase the risk of the disease white spot (or `ich’). If everything is working well, purchase your first few fish.

Water is Heavy

4.5 liters of water weighs more than 4.5 kilograms and when you add the weight of the tank and the gravel, the average weight of the aquarium is more than 4.5 kilograms per 4.5 liters. A 45-liter aquarium, for example, will weigh about 60 kilograms. Its support should therefore be sturdy. Avoid direct sunlight
Most aquarists prefer to avoid exposing their aquariums to direct sunlight. Although it does not affect the health of the fish directly, it tends to promote the rapid growth of algae which is undesirable because it creates unnecessary maintenance problems.

Selecting the Aquarium

When you have decided on the type of fish you want to keep, your next question is how many? These two factors will determine the minimum aquarium size. The rule of thumb for small freshwater fish is to allow 2 liters of water for every centimeter of fish; for marine fish, 10 liters per centimeter. Your first tank should be at least 45 liters, preferably larger. This allows a greater choice of fish and plants and requires less maintenance. A tropical fish tank: Note the healthy appearance of the tank in general.
The capacity of an aquarium can be measured by multiplying the height and width in centimeters and dividing by 1000. This gives the _ tents in liters. Allow for any rocks or ornaments in the aquarium; the:it usually occupy about 10 per cent of the volume.
The height of your tank should be no more than 20 per cent greater than the width, otherwise the surface of the tank will be too small to allow the water to absorb sufficient amounts of oxygen. A rule of thumb is 65 square centimeters of water surface for every 2.5 centimeters of fish length.

Other Necessary Equipment

Cover and Lighting
Covering the aquarium is necessary for several reasons. It saves money by reducing heat loss. By keeping the air temperature above the water the same as the water temperature, the water will stay warmer and will not overwork the heater. The cover also slows down the rate of water loss by evaporation. A cover prevents your fish from jumping out or friendly pets from jumping in. It also stops aerosol insecticides entering the water. A cover also serves as a holder for your lighting.

Thermostatic Heater

Unless you plan to keep only coldwater fish, the aquarium will require a thermostatically controlled heater to maintain the water at a tropical temperature. Heaters vary in cost, accuracy and reliability, but always purchase the best you can afford.

Filtration and Aeration Equipment

The major objective of all filtration systems is clear water plus aeration. If the water circulates from the water surface throughout the aquarium, you will have good aeration. One device used to encourage water circulation is an air stone. Placed on or near the aquarium floor, the porous air stone releases bubbles which push bottom water to the surface and create a circular flow. Because the water will circulate debris from the bottom as well, the air stone should be placed 5 centimeters above the gravel. The force of air rushing to the surface is often coupled to a filter by means of an airlift. The airlift is a tube that confines the air bubbles and uses them to force water through the filter. Filter systems vary in cost and complexity, and it is best to consult the pet shop dealer for advice on the one most suited to your needs.

Sand or Gravel

Whether you choose natural or colored sand it is best to obtain it from your pet store. If the gravel is artificially colored, make sure that it is non-toxic and colorfast. As a general rule you will need approximately 1 kilogram of sand for each 4.5 liters of water in the aquarium.

Ornaments, Rocks and Plants

Driftwood, petrified wood, bamboo cane and non-metallic rocks are generally safe in an aquarium. Metals other than stainless steel can poison your fish. Some objects (coral, limestone and marble, for example) will dissolve in fresh water and thereby change the water chemistry. Plants add color and beauty to an aquarium and, very importantly, they offer areas of retreat for the fish. You can use living plants, artificial plants or both. Live plants have advantages and disadvantages. The advantages: Besides being more natural, they compete with algae for nutrients. Their very presence will help reduce or eliminate algae problems. Along with this, they absorb nitrates and slow down the nitrate build-up. Nitrates are waste products and in large quantities are toxic to fish. Plants are also a food source for a number of fish. The disadvantages: Plants are often difficult to grow, requiring specific water conditions and lighting. Decaying plants increase pollution in the aquarium, so any that turn brown or start to disintegrate should be removed quickly. Plastic plants can relieve that barren time when live plants are establishing themselves.

Water Conditions

The pH level (acidity/alkalinity) The pH level is particularly important for maintaining and breeding fish. Some fish species prefer alkaline water while others prefer acid. pH levels can be altered by chemicals: use sodium biphosphate for increasing acidity/ lowering alkalinity, and sodium bicarbonate for reducing acidity/increasing alkalinity. Excessive alkalinity or acidity for freshwater fish can also be reduced by the use of bottled water. It is best, however, to adapt the fish to the tap water in your community. A pH level between 6.8 and 7 suits most tropical fish; 7 to 7.2 suits Goldfish; and 8 to 8.3 suits most marine fish.


Tap water, like natural water, varies in hardness from area to area. `Hardness’ refers to the dissolved salts in the water, mainly those of calcium. sometimes also magnesium. Many tropical fish prefer a relatively soft water. White deposits at the water line are a clear sign of high hardness. Hardness s can be reduced by regularly replacing part of the water with aged tap water—the water is aged by allowing it to stand exposed to the atmosphere for one week. This does not decrease hardness if the tap water itself is hard. Then the water needs to be filtered through peat or Zeocarb 225. An occasional hardness test is a good idea, as sometimes a rock or the gravel in the tank can cause a problem. The hardness level should ideally be below 100 parts per million, except for the few fish species that thrive in hard, alkaline waters. Water can be softened by using an ion exchange resin such as Zeocarb 225. The most logical approach is to remove the hardening factor—that is, the rock, gravel or whatever, from the tank. There is no place for coral or seashells in freshwater tanks because of their hardness factor.

Selecting the Site of the Aquarium

Temperature control is important

Direct sunlight may overheat the aquarium. Overheating can also be caused by closeness to room heaters. Do not place the aquarium close to air conditioning units, open windows or outside doors either. Changes in water temperature greater than 2°C above or 1°C below the optimum temperature for the type of fish you are keeping can cause shock and illness.

Will the tank be accessible?

The final consideration in assessing the site for your aquarium is whether you can easily reach your heat controls and air valves.

New fish

Ideally new fish should be quarantined for up to six weeks in a tank reserved
for this purpose. Use the transfer methods already described when introducing
them to the main tank.

Transferring the Fish

There are two methods commonly used to introduce fish into the aquarium. One way is to transfer the fish into separate glass jars, and float the jars in the aquarium for fifteen to twenty minutes. Make certain the jars do not have so much water in them that they sink. Every few minutes add small amounts of aquarium water to each jar. After the water temperature in the jar is the same as that in the aquarium, tip the fish into a net and release it into the aquarium. Do not pour water from other tanks into your aquarium as it may introduce unwanted organisms. The second method uses the plastic bags in which the fish are usually transported. Use the same floating technique, making sure that there is plenty of air in the bag so that the fish do not suffocate. Do not allow the bags to collapse. These methods are tedious, but they will reduce the initial shock to your fish in their new environment.
The reason for introducing only a few fish at first is to initiate the nitrogen cycle, which takes at least twenty to twenty-five days to stabilize. More fish should not be added until the nitrite level has dropped to a safe level otherwise the fish will die. Nitrite test kits are available from pet shops.

Regular Water Changes

A weekly water change of approximately 20 per cent with water of the same temperature is advised. For freshwater fish do not use water from the hot water system as it may be contaminated with copper. The water to be changed should be siphoned from the bottom, making sure that the gravel is gently agitated and that any algae that has accumulated is removed with the water. If the water is very soft, the addition of half a teaspoon of common salt with a pinch of both magnesium sulphate and potassium sulphate is recommended to each 5 liters of replaced water. Temperature and pH should be checked and adjusted if necessary.

Signs of Trouble

As you come to know your fish, there are several signs that may indicate trouble on the face of the water, it can mean that the tank is not getting enough oxygen. This may be due to inefficient or clogged filters, water pollution (due to excess particles of decomposed food), poor aeration or overcrowding. This is serious and requires immediate action. Change at least one-fifth of the water in the tank, replacing it with water of the same temperature. Clean and replenish the filter, siphoning off excess .food. Increase aeration and reduce the number of fish. Another danger sign is cloudy water. This usually results from excess feeding. Never tap on the glass side of the aquarium, as this is like a sonic boom to the fish and can cause them to go into shock.


The amount of dissolved nitrites and nitrates in the water is a direct indication of the level of water pollution. High pollution levels impair the health of fish and can be lethal. Chemical kits for testing the pH, hardness and pollution levels of nitrites and nitrates in your aquarium are available. They should be used regularly. To maintain a low nitrite/nitrate level it is essential to change part of the water regularly.

Feeding and Control

It is advisable not to feed the fish until they have adapted to their new environment. Watch them closely; if they are hiding in corners, not moving about or looking pale, something is out of order. Recheck your establishment procedure. Is the temperature correct? Was the water too fresh? Is the lighting level in part of the tank too high? Are there sufficient plants to provide hiding for the fish? Are the fish healthy?


Tropical and Goldfish tend to be good eaters, while marine fish can be a little fussy. Generally, tropical fish, Goldfish and marine fish can all be fed a similar diet, and there is a wide range of adequate economical commercial fish foods available. The following is a list of some foods of particular delight to each group.

Tropical and Coldwater

Food for tropical fish should be high in protein, low in fat and oil. Trot and Goldfish will all eat kangaroo meat, horse meat, earthworms, moss, larvae, slaters, house flies (without insecticide), rolled oats, lettuce, spin crushed peas and broad beans. Do not feed mutton or mince meat. Marine Marine fish are particularly partial to dry flake food, shrimps, tubiflex, of fresh meat, ground beef, heart, prawns and Pacific plankton. Marine ±Al are fussy and may prefer chunks, strips, mashed or ground food. When else fails, offer live food. They love fresh, live, adult brine shrimp.
There are three basic rules about feeding fish: (1) Feed sparingly often. If all the food is not eaten within five minutes of feeding, you might be providing too much and the residue will pollute the aquarium. (2) the kind and shape of the food if the fish are not eating it. (3) Be careful with fussy eaters and resort to live foods if necessary. Avoid continually modifying the aquarium conditions. A stable environment develops a necessary sense of security. Avoid overcrowding. Calculate how much your aquarium can safely keep—remember, for small troy fish, 2 liters of water for every centimeter of fish—and always have fewer than that.

Brackish Water

Most Catfish will tolerate slightly brackish water such as that containing half a teaspoon of salt, a pinch of potassium sulphate and one of magnesium sulphate per 5 liters of water, as recommended. Most of the common aquarium Catfish (and the Discus) are derived from high up the Amazon River where the water is very soft, very low in salt and very acid. These fish are bred in water containing these quantities of salts at a pH of 6.8 and a temperature of 24-26°C—although the purists may prefer a pH of 6.2 and a temperature of 29-31°C in water containing no salt. Live bearers such as Mollies, Swords and Platys appear to suffer more from lack of salt than do Corydoras and Discus, from the addition of the above quantities.

Controlling Snails

Sooner or later water-snails, the uninvited guests, will appear in I aquarium. They find their way into the tank with plants or with live foci. It is not necessary to use snails for cleaning up excess food and algae. In fact, hungry snails will eat your aquarium plants. A rapid increase in the snail population is a sure sign of overfeeding. If snails should breed beyond control, do not use chemicals to get rid of them, as dead snails will only foul the water. It is better to feed for the next few weeks and effect a natural control. Alternatively snails ma: be picked out with a long pair of clean tongs. Another method is to limit feeding for a few days, then place a saucer on the bottom of the aquarium upside down with some food underneath; the snails adhere to the saucer and can be removed with the saucer.