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Keeping Tropical Fish

Updated on September 19, 2010

Keeping tropical fish is a fascinating hobby, for the well-stocked tropical aquarium is a constant source of interest as well as a decorative addition to a room. Not only are the fish brilliantly coloured, they are also clean and silent, ideal pets which will thrive if looked after properly.

Although this article is concerned with looking after a tropical tank, the general advice on setting up and filling the aquarium applies equally well to a cold water tank. In either case, bear in mind before you start that keeping an aquarium demands a good deal of preparation and quite a bit of regular care and attention; certainly more than keeping a canary or budgerigars. But while a caged bird can safely be taken to a friendly neighbour when you go away for a holiday, an aquarium cannot be. If you have to go away and cannot get someone to come in daily and feed your fish, it is probably best to scoop them out with a net and have them cared for by a friend who has an aquarium. All these things need considering before you start keeping tropical fish.

Photo by Adam Jakubiak
Photo by Adam Jakubiak

Decide first on the size and kind of aquarium you want. The number offish you can keep without artificial aeration (that is, using a pump to bubble air into the aquarium) depends on the area of the water surface. For fish up to 5 cm long, reckon 15 fishes per 1000 square centimetres of surface area. So an aquarium 50 cm X 30 cm has a surface area of 1500 cm2 and will hold up to 22 fishes. (Note: in a cold water tank, without artificial aeration, assume 2 litres of water for every centimetre of fish. A goldfish 5 cm long needs 10 litres of water in order to have enough room to feed, breathe and grow normally.)

The commonest kind of aquarium is made of clear glass sheets cemented into an angle-iron frame, and it should have a glass cover or a metal hood. It should not be stood in the window, or it will get too much light. Against a wall opposite the window is better, so that daylight falls on the front. Against a side wall, or even in a niche or alcove, is all right if you are prepared to keep the artificial lighting —which you will need anyway — switched on for some eight hours daily. The place chosen should be near an electric power point. The aquarium can be stood on a piece of furniture, but it must be a solid piece as it will have to carry 50 kilograms or more. Otherwise you will have to buy a special stand with the aquarium. If the aquarium is to stand on a piece of furniture, first cover this with a sheet of hardboard cut to the size of the base.

A new aquarium should be tested for leaks by putting it on the floor (out of doors), filling it with clean water and leaving it to stand overnight. If it leaks, it is probably best to take it back to the dealer. Any repairs must be made with aquarium cement as other cement can poison fish. This test filling also serves to wash out the aquarium; but never use soap or detergent for cleaning. Empty the aquarium by baling it out; never by tilting and tipping, as this will strain the frame and cause leaks.

Before the aquarium is finally filled the electrical connections must be made. Seek expert help to make sure this is done correctly. The lighting, thermostat and immersion heater need connecting. The lighting is required not just to show up the fish but as artificial sunlight for them and the plants. Some aquaria have strip lighting built into the hood, but for those with a glass cover a 6o-watt bulb fixed about 10 cm above the water is needed, with a separate switch. The thermostat controls the heater by switching it on or off according to the temperature of the water. It should be hung in one of the back corners of the aquarium, with the heater in the other. Heating is required because tropical fish need to live in a temperature of about 24°C, which is a good deal warmer than even a centrally heated room.

Water for the aquarium can be drawn from the cold tap and mixed half-and-half with clean rain-water. Do not use water from a pond or household water softener. By standing the water outside in plastic or enamelled-iron buckets (never use galvanized buckets) for two or three days, it becomes aerated. Also, the tiny animals called infusoria which float in the air, fall into the water and develop; they are useful food for small fish. For an aquarium 50 cm by 30 cm you will need about 40 litres of water. You will also need about 5 kilograms of sand.

Aquarium sand is actually a fine gravel. It should first be washed by putting it into a bucket of water a few handfuls at a time and stirring well. The muddy water should be poured off and the process repeated until the water runs off clean. The sand must be placed in the aquarium so that it is about 8 cm deep at the back and 3 cm at the front. A few rocks should be added; but see that they are clean (wash them in hot water), and do not use limestone rocks such as marble. The tank can now be filled half-way up. So as not to disturb the sand when you pour the water in, lay a saucer on it and then pour slowly into the saucer.

The aquarium must now be planted. The object of this is not only to give the fish more natural surroundings and to improve the appearance, but to help aerate the water. Fish extract oxygen from the water and breathe out carbon dioxide, while plants extract carbon dioxide from the water and (by day) give off bubbles of oxygen. Recommended plants are Sagittana, Vallisneria, Myriophyllum, Elodea, Ambulia, Cabomba and Cryptocorine, though the last-named is rather expensive. Some of these have roots above which is a "crown" from which all the leaves spring. Using a notched stick, push the roots into the sand until the crown is left just showing. The others are sold as cuttings, which are lengths of stalk that only need pushing into the sand. Wash all plants first in running water and pick off any snails.

Do not plant your aquarium too thickly, but leave the fish plenty of swimming-room where they can be seen. Plants put in the shallow sand in front may not grow well, and if they do they will shut out your view of the fish. When you have finished planting, fill the aquarium completely and plug in the heating and lighting, as the plants (like the fish) need both warmth and light. Now check the working of the heater and thermostat, using a floating thermometer which should remain in the aquarium. Adjust the thermostat so that it keeps the water temperature at a constant 24°C. Allow a few days for the plants to settle in.

After all this work, the aquarium is ready for the fish. Some fishes are expensive, and it is best to start with a few cheap ones to make sure that the conditions in your aquarium are correct. The larger kinds (more than 8 cm long) are not suitable for an aquarium whose surface area is 1500 cm2. Moreover, some of the larger fishes will gobble up the smaller kinds. Small tropical fish that live peaceably together include guppies, flame fish, black mollies, platys, the smaller kinds of barbs and gouramis, the very hardy White Cloud Mountain minnows, neon tetras, bloodfins, pearl danios and angel-fish. Generally speaking, fish should be bought in pairs (male and female), as single fish tend to mope. The exception is the small catfish. Many aquarists like to keep one of these little whiskered fish, as it acts as a scavenger, grubbing on the bottom during the night for scraps of food unwanted by the other fishes and thus preventing the sand bed from caking. Others prefer water snails for scavenging, but snails tend to nibble the plants and breed very rapidly.

Most dealers supply fishes in polythene bags with a little water and the space above it filled with oxygen. It is important that bowls or bags should not be chilled on the journey home; carry them in a box or basket packed with crumpled newspaper. You can use a vacuum flask for carrying, but it has only enough water surface area for two fish. A bag or bowl in which fishes are carried should be floated in the aquarium for an hour before it is tilted to let them swim out; this allows the temperature to equalize gradually.

The prepared fish foods sold in packets or cartons provide a balanced diet. Keep them in a dry place with the containers firmly closed. An occasional change of diet can be made by feeding shredded shrimp and Daphnia (water fleas), which can be bought from pet-shops; or cooked foods such as lean meat, chicken, liver and cod's roe, which must be finely divided or chopped up small. Small pink earthworms can be given, but they must be washed in running water before and after chopping up. Fish get some green food from algae, which is the simple plant life that grows in almost all water, but you can give them chopped lettuce leaf or duckweed collected from a pond.

Feed the fish once a day. Great harm can be caused by overfeeding, not because the fish over-eat but because the food they do not eat decays at the bottom of the aquarium and poisons the water. (A sure sign of the start of this is blackened patches on the sand.) Give the food a pinch at a time and watch to see how fast it is eaten. The amount you give should be such that all of it is eaten within five minutes. Fish in good condition can be left unfed for a day or two, so it is safe to leave them for a week-end, though not longer. (The heating must then, of course, be left on, though the lighting should not be.)

The time for which the lighting is kept on can be judged from the state of the plants. Rapid straggly growth and yellowish leaves usually mean there is too much light, as does a rich growth of green algae on the glass and rocks. If the plants become brownish in colour and do not seem to thrive, increase the period of lighting or use a stronger bulb. Dead leaves should be removed. Plants that have grown until they are trailing across the surface should be cut back.

Every week or so, remove algae from the glass by scraping with a razor blade in a cleft stick. If the aquarium has a Perspex panel, use a clean dish-washing mop for this. The fishes' droppings and dead fragments of plants settle on the sand to form a muddy-coating called mulm. This must be removed, with any dead leaves, scrapings of algae and blackened sand. You can do the job with a glass dip-tube. Place your finger firmly over the upper end to seal the tube, then dip the tube into the water above the debris to be removed, keeping the finger firmly on the other end until the tube is in position. Remove your finger and the debris will be sucked into the tube. Replace the finger on the upper end and remove the tube; to release the debris, remove the finger from the tube. Another way is to use a length of rubber tube as a siphon. (For more information, see siphon.) Lower one end of the tube into the aquarium, hold the other end at a level below that of the water and suck it. When the water comes, drop the sucked end into a bucket on the floor. Now use the end in the aquarium like the nozzle of a vacuum cleaner to suck up the mulm. Naturally it sucks up a good deal of water too, so when the mulm has settled strain the water in the bucket through a clean piece of nylon torn from an old shirt or blouse and return it to the aquarium.

If the water turns green, as it may sometimes in summer, the cause is almost certainly a rapid growth of algae due to too much light. But if the water turns cloudy or milky with an unpleasant smell, the trouble is probably overfeeding. You can stop feeding for a day or two and hope for the best, but it is likely that the damage has already been done and that some fish will have died. All you can do is to catch the survivors in a net and put them into the largest container you can find, filled with water at the correct temperature. Then you must bale out the aquarium, remove everything from it and have a thorough clean out, starting again with clean sand, washed plants and rocks and a fresh supply of water.

Do not let visitors tap on the glass with the idea of attracting the fish. It does exactly the opposite; they dart off and hide, and in doing so may injure themselves by knocking against the glass or rocks.

If you have male and female fish of the same kind they will probably breed, although some fishes require warmer water for breeding and unless special precautions are taken the young may not survive. For successful breeding you really need more than one aquarium, and it is best to consult a book before going in for this. The librarian at your local public library will help you.

Hints on keeping Tropical Fish

DO prepare carefully and thoroughly.
DON'T overcrowd your aquarium.
DO first test for leaks by a trial filling.
DON'T empty the aquarium by tilting it.
DO use a firm strong base for the aquarium.
DON'T make electrical connections yourself.
DO wash sand, rocks and plants first.
DON'T plant too thickly or along the front.
DO start with a few of the cheaper fishes.
DON'T on any account overfeed the fish.
DO clean the aquarium regularly.
DON'T let people tap on the glass.


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    • profile image


      8 years ago

      i want a fish tell me moor

    • 2besure profile image

      Pamela Lipscomb 

      8 years ago from Charlotte, North Carolina

      Great article more pictures of fish pleeeease! They are so beautiful. My favorite are betas.

    • caninecrtitics profile image


      8 years ago from Massachusetts

      Just to let you know that fish picture is a cardinal which is a saltwater fish.

    • Abbirocker99 profile image


      8 years ago from 19

      Great Job on this


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