Buying your fish

When purchasing a fish, you should look for a specimen that shows erect fins, bright colors and which has a well fed look. Avoid fish that have sunken bellies or those that constantly rub themselves against rocks, as this could be a sign of irritation caused by some disease. If any of the occupants of a tank look sick or thin, it is likely that all the fish are carriers even though the disease may not be evident in all the fish in the tank. When purchasing for the first time, do not be persuaded to buy species about which you know nothing. It is better to go out with the intention of buying specific species that are known to be compatible.

Try to buy locally - the journey home will be shorter and the shock to the fish will be much reduced. Take a polystyrene lined box with you to help retain the heat in the polythene water bag. Avoid unnecessary jarring and vibration and handle your fish carefully. Choose specimens that are bright and active. Before leaving the shop, get as much information as you can. Find out how long the fish have been at the shop, where they came from, what they are eating. Also enquire about the pH level of the water in which they have been kept. Observe whether they are aggressive towards other fish and whether they have territorial inclinations.

It is far better to make a preliminary sortie to the shop on a fact-finding mission. Discuss with the shop-keeper the fish that you intend to purchase. Most are delighted to discuss all aspects of fishkeeping with a prospective customer. After all, you may become a regular purchaser at the shop which gives you an informed and personal service. Beware, however of the dealer who is not prepared to discuss his fish with you. There are some dealers whose knowledge is not what it should be and whose only purpose is to make a sale before their badly kept fish die in their tanks. Fortunately, these dealers are in the minority and their policy is a short signed one as the buyer will not return to their shop again.

If you follow the principles of good purchasing and set out to buy only the species for which you have planned a home for, then you should not encounter any problem that cannot be solved by careful maintenance.

When you return home with your purchases, they should be introduced to their new environment gradually. The room lights should be dimmed and the tank lights should be switched off. The polythene bag containing the fish should be floated in the water for about 20 minutes to allow the water temperatures to equalize. Remember to open the top of the bag or the fish may suffer from lack of oxygen. Allow the water in the bag to mix gradually with the tank water and avoid any sudden change which might occur if the pH factors vary.

Newly introduced fish usually seek the shelter of plants and they should be left alone for a few hours, after which they may be coaxed from their cover by offering tempting morsels of food. Any food left uneaten should be siphoned from the tank to avoid pollution. Remember to drop the food over a clear spot on the tank so that it can easily be removed if necessary. 

Keep watch on newly purchased fish to see if they are aggressive, or worried by other fish. If they are not compatible one or another of the fish should be moved to another tank.

A well balanced community of fish can be obtained by choosing a mixture of bottom-living species, shoaling midwater species and surface-living species. In this way, they each have their own territory and the tank has a well filled look. Where possible you should try to buy fish in pairs, or even more with a shoaling fish.

Although most species of fish can be safely kept together, there are species which are not recommended for the normal community tank.

When you make your choice of fish for the aquarium, there are two important considerations that must be borne in mind.

First is the maximum number of fish that your aquarium will safely contain, for if you overstock, then there will be insufficient oxygen and they will soon be gasping at the surface. For tropical aquaria, you should allow approximately 25 inch (63cm) of fish (combined lengths) to each square foot (929 sq cm) of surface water. You can assess the fish lengths on the sizes given in the Identification guide for adult specimens, remembering that the young fish you buy will soon grow if you care for them properly.

The second consideration is the characteristics of the fish you select: it is not just whether they will all live peacefully together that is important, but the overall effect that will be created in the aquarium. If you are setting up a community aquarium you will want fish at swimming all levels: some staying mainly near the surface, others in mid-water, and a few remaining near the bottom. You will probably also want fish with a wide variety of behavior patterns: for instance some being fast-swimming shoaling types, others being more solitary in their activities.