Popeye disease, also known as exophthalmia, is when a fish’s eye bulges from its face and becomes cloudy. It is a symptom of a fish disease rather than a condition and is caused by poor water quality, injury, and/or bacterial infection. It can cause the fish to lose its sight, and possibly eyes. Popeye is not extremely contagious, but quarantine is best, just to make sure.
Treating Angelfish Eye Disease: Pop-eye
Check water quality for nitrites, nitrates and ammonia using a water testing kit like this one. Some cichlids, such as angelfish, are sensitive to poor water quality which can cause pop-eye. For an angelfish eye disease, even if water quality is acceptable, a water change is indicated. If the fish is kept in the tank, 50 percent daily changes for 4 or 5 days are recommended. Poor water quality can lead to bacterial and fungal infections.
If only one eye is infected then it is likely the result of an injury. In this case, move your angelfish to a quarantine tank and do a salt dip for treatment. Treat with a tablespoon of aquarium salt per 5 gallons of water.
If both eyes are infected, it is possibly a bacterial infection. The best treatment then is to move the infected fish to a quarantine tank, and treat with Maracyn or Maracyn II, or broad spectrum antibiotic.
Popeye fish disease is treatable, and the sooner the problem is identified, the better chance of success.