The health section

Fish are living things and they occasionally suffer from poor health for a variety of reasons. This section describes how to proceed when you notice that one or more of your fish is ill.

Always check the water quality before anything else. In the majority of cases it is water chemistry or water quality which is the cause of the illness. If you ask for help on a fish forum always print a recent set of accurate water test results if not you will be asked for them and valuable time will be lost. Don't try to avoid this by saying "my water is fine" again valuable time will be lost as a result.

A comprehensive set of water test kits is an essential part of fish keeping, you will need kits to test for:

Ammonia
Nitrite
Nitrate
pH
KH
GH

Liquid reagent test kits are far more accurate than paper test strips which generally are not accurate enough for diagnostic purposes.

The worst thing you can do is treat the fish with the wrong medication, you should wait until you know what is wrong with the fish before treating and then use the correct and most effective available treatment .