When setting up a tank you must be careful which fish you buy. Not all of them are suitable as tankmates. Not all fish sold as ‘community fish’ are necessarily suited to others.

A good guide, apart from the potential size of the fish, is to look at their tails. Fish with streamlined bodies and small, pointed fins and tails will be quick swimmers which dart about and will always be first to the food.

A fish with a rounder, fatter body and longer, flowing fins, will be a slow mover. These fish, unable to keep up with the faster ones, often miss out on the bulk of the food as the quicker fish will have eaten it before they get there.

Many of the faster fish (particularly tetras and barbs) are well known fin nippers. Putting them in a tank with a lot of inviting, drooping fins and tails is asking for trouble as they can’t resist a nibble as they swim past.

Many fishkeepers mistake nipped fins for fin rot and desperately drop medications into the water and wonder why the fish don’t improve. Fin rot will tend to go right to the base of the fin, often accompanied by red streaks of blood. Next time you reach for the fin rot medication, check out the tank mates first and consider if one of them may actually be the culprit.