Pop Eye
Exophthalmus; Corneybacteriosis; correct term can vary, depending upon exact cause
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Description:
Pop Eye itself is not a disease, but a condition resulting from one of several possible problems: a bacterial infection (it can contract fungus as a secondary infection afterwards) environmental problems (poor water quality, etc) or trauma to the eye via an accident or injury from an aggressive tankmate. The fish may appear to have a large clear bubble over one or both eyes. The eye(s) will protrude out from the fish's head and may also be cloudy.
Treatment:
Only one eye bulging typically indicates that the problem has occured due to an injury to the eye somehow: the eye responds by swelling and retaining fluid buildup. Quarantining the fish and giving it clean water will help it to heal on its own with a little bit of time and isolation to reduce stress. Epson salt can help (1 tablespoon per five gallons; repeat with a half dose on day three as per WetWebMedia).
If both eyes exhibit symptoms, it is probably a bacterial infection. Treat with medication such as Maracyn, Penicillin, or Tetracycline. Neomycin sulphate (use 250 mg/gallon) is an antibiotic which is affective against a wide range of gram+ and gram- bacteria. You can find other broad spectrum antibiotics here. In advanced stages if there is a deep bacterial infection, it can be difficult to treat. Feed medicated food to the fish (it can be hard to get antibacterial medication inside the fish; most simply won't absorb). Medicate with antibiotics in a hospital tank to prevent damaging the biofilter in tanks. Read here for more on bacterial infections.
