Fish Is a Veterinary Animal Part 2. Examination of Fish

When an appointment for a sick fish is made, ask the owner to bring two separate samples of water, one directly from the (bio)filter and one from the aquarium or pond.
The first approach to a fish problem is taking the history from the owner.

Examination of the patient

Then look at the fish for abnormal swimming behaviour, abnormal colouration, abnormal body form, frayed fins, bulging eyes, wounds, tumours, etcetera. If possible observe the fish in its own aquarium or pond.

Water samples

From the water samples at least the pH, ammonia and nitrite level must be measured. Ammonia and nitrite are very toxic to fishes and should not be present. There should be a difference in the ammonia or nitrite evels in the water sample from the filter and the one from the aquarium or pond. When both samples contain too much ammonia or nitrite, the biofilter is not functioning properly. Then one or more partly water exchanges are necessary to improve the living conditions for the fishes. The cause must be found and dealt with. Before any medication can be put into the water, the water quality has to be optimal. pH, temperature, hardness, oxygen and nitrate level are also important parameters. [...]