The problem is called pop eye.
Pop eye fish disease is various combined problems and or symptoms of an underlying disease,he most common being bacterial infection. Bacterial infection may have been caused by some preceding fish diseases or ailment. It can also be caused by rough handling, tumors, too much lighting, poor dietand or a vitamin A deficiency. The eyes begin to protrude and a build up of fluid forms in and around the eyes. Like most fish disease, stress is one of the main factors. Overcrowding, poor water quality and temperature changes in the aquarium are all major causes of stress in your freshwater fish. Good water quality is a must for keeping your freshwater cichlids healthy. Rarely life threatening, pop eye fish disease is easily curable. However, sometimes the fishes eyes will not fully heal and may remain a little bigger than usual, even after the fish has recovered fully.
Symptoms of pop eye disease are one or both eyes will appear a lot larger than normal. Pop eye fish disease will cause the eye or eyes will protrude from the head and look as if the eyes have a cloudy covering. The disease takes about two weeks to peak, and by then the eyes have swollen a great deal.
when treating pop eye disease you must make sure your aquariums water quality is in good shape. Also, check you tanks parameters such as ammonia and ph. If these check out okay you can proceed with the treatment. It is best to treat your aquarium with a broad spectrum antibiotic. Antibiotics can treat a large range of ailments in your freshwater fish. Always check the water quality first. Often times it is the root cause of fish disease in aquarium fishes. When treatment fish diseases, I use a bare-bottomed hospital tank with no decor and very little light. This tank is also in a room that receives very little traffic, therefor the odds are disturbing or stressing the fish is low.
This is what i found about this disease.
I sugest start regular water changes as sugested before,i don't like to add medicines to my tank,but if the problem remains you can go for the antibiotics.DO you have a way to separate him from other fish?
If you use the medicine after treatment use activated carbon to remove it from the water.
hope this helps
