Caring for your goldfish

In our last 'Pet Den' page, our veterinary surgeon, Dr. D.A.U. Samankumara of the Kirindiwela Animal Clinic told you how to prepare the tank for fish and what you should know when buying fish.

Today, he'll give you some more important facts on how to breed goldfish. First of all, he'll tell you how to mix goldfish with other fish varieties.

An aquarium where many varieties of fish live together is called a community aquarium. Fish are on a race for oxygen, food and space. The fish that we put together in a tank should have the ability to face this race. So, we should not put small and big fish together because the small fish might lose the race.

We also must not put fast and slow swimmers together; e.g. the lionhead goldfish is a slow swimmer whereas the fantail goldfish is a fast swimmer. If the two are put together, the lionhead goldfish will lose in the race for food.

Mixing goldfish with other species of fish or animals is not recommended either. This means, goldfish should not be mixed with Angel fish, Guppi or tortoises. Most other fish varieties are tropical fish, but the goldfish lives in cool water.

As we mentioned in our previous article, goldfish live in temperatures of 22 degrees Celsius, but most other fish need water at higher temperatures. So, it's not really practical to mix other varieties with goldfish. You should not put goldfish with aggressive fish like Angel fish as well; they will attack the goldfish.

Most fish are disease carriers. The diseases may not affect the carriers, but will affect the other species.

How to maintain a fish tank

The easiest way to keep the goldfish healthy is by preventing them from catching diseases, rather than curing them later. Disease-causing organisms are bacteria, fungi, viruses and ecto and endo parasites.

No matter how clean a tank is, it will have disease-causing organisms living in it. But, the fish may not get the disease. For example, organisms that cause white spot disease or fin rot are present in most aquariums, no matter how healthy the aquarium appears to be, and no matter how well it is maintained. These organisms are inactive until the conditions become right for them to grow and multiply.

A weak or stressed goldfish is the right condition. Environmental stress such as foul water, over-crowding and poor diet are major causes for the goldfish falling sick. Environmental stress can be eliminated by a good aquarium management programme.

This programme is not complicated and does not require a lot of work. You must buy good quality equipment and must check whether they are in good condition, regularly. The air system and filter apparatus must be checked once a week.

How to change the water

Fish waste, leftover food, dead fish and plant leaves usually accumulate on the tank floor. These waste material decompose or rot, releasing poisonous chemicals such as NH3 (ammonia) and CO2 (carbon dioxide). If there is a good filtering system, these gases will be removed.

These chemicals usually increase the acidity of the water. When the water is acidic, the NH3 accumulating in the tank is locked up in another form which is harmless to the fish.

When the water suddenly changes from an acidic to a neutral or alkaline composition, a lot of locked up NH3 is released as free NH3. This free NH3 is poisonous to fish. So, we should not remove all the water in the tank at once, but 1/4 or 3/4 of water should be replaced once a week. That will provide a good environment for the fish.

When mixing new water into the tank, also ensure that it is the same temperature as the water in the tank. Or else, the fish will die of temperature shock. Next day, we'll tell you about fish food and feeding....

Janani Amarasekara