Instructions
Inspect your fish's scales for wounds, discoloration and growths. Missing scales could be a sign of fighting.
Observe the fish's respiratory rate - if it's slower or faster than normal, that could indicate problems.
Check the clarity of its eyes. There should be no blood or cloudiness.
Look for abnormal behavior, such as sluggishness or an unusual swimming pattern.
Consult a veterinarian.
How to Tell if Your Tropical Fish Is Sick
If your fish appears sick, examine the water quality, diet and social structure of fish in the aquarium. It helps to know what's normal in order to determine what's not.