A single cloudy eye could be the onset of a debilitating disease, or parasitic attack (e.g.,
Cryptocaryon irritans), an indication of poor water quality (ammonia), or nothing. On the ââ"šÂ¬Ã‹Å“nothingââ"šÂ¬Ã¢"žÂ¢ side, it could be the fish injured the eye in a mild fight with a tankmate, net damage, ran into some decoration in the tank, or managed to pick up a mild bacterial infection.
All of these ââ"šÂ¬Ã…"œone-cloudy-eyeââ"šÂ¬Ã‚ situations are ââ"šÂ¬Ã‹Å“probablyââ"šÂ¬Ã¢"žÂ¢ not worth taking any specific action as far as the fish is concerned. You can help out by making a large water change with properly mixed and aged saltwater. The second thing you can do is make sure youââ"šÂ¬Ã¢"žÂ¢re providing the proper nutrition to the fish. See this post:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=785228
The fish should be closely watched for whether the eye is healing or getting worse. The fish should also be watched for any other symptoms of disease. Besides a water change and upgrading the food (see above) there are other things you can do:
Check all water quality parameters. Monitor ammonia especially an hour after feeding. If water quality is eliminated for sure, then make sure there is no decaying matter in your system to address a possible bacterial issue. Time to do a thorough cleanup. This can reduce the numbers of bacteria in the water column. In addition to checking ââ"šÂ¬Ã‹Å“the usual suspectsââ"šÂ¬Ã¢"žÂ¢ with regard to water quality, also check for dissolved organics.
You want to have a treatment tank/quarantine tank standing by, and in case things get worse, youââ"šÂ¬Ã¢"žÂ¢ll need to put the fish into quarantine. A great, comprehensive guide on quarantine tanks and procedures can be found in this article:
http://reefkeeping.com/issues/2004-10/sp/feature/index.htm
If the eye is cloudy AND there is obvious swelling, then besides a bacterial issue, it could also be a parasite. From the photo you provided, your fish has not only a cloudy eye, but a swollen eye. This is a grey area ââ"šÂ¬Ã¢â‚¬Å“ you can play the ââ"šÂ¬Ã‹Å“wait-and-seeââ"šÂ¬Ã¢"žÂ¢ game (while improving its diet and water quality) or you can go ahead and give the fish an antibiotic treatment, just to be sure it doesnââ"šÂ¬Ã¢"žÂ¢t get any worse (see below). This is assuming there are no other signs of any other disease or condition. If a parasite is suspected to be attached or in the eye, a fresh water dip might knock it off.
If your fish has
two cloudy eyes, and/or a condition of Popeye then this is something to be more concerned about, IMHO. Itââ"šÂ¬Ã¢"žÂ¢s not likely it ran into something twice, on each side, or hurt itself symmetrically. The suspicion of disease now goes high. If you can see no other symptoms of disease, the fish with two cloudy eyes or Popeye should be moved to a treatment tank and treated with an antibiotic, IMHO.
A fish with two cloudy eyes from a bacterial infection shows there is something ââ"šÂ¬Ã‹Å“offââ"šÂ¬Ã¢"žÂ¢ for sure. There is always bacteria in our tanks, but healthy fish keep it at bay. And in a healthy tank, the bacterial population in the water column, isnââ"šÂ¬Ã¢"žÂ¢t high. When a fish gets a cloudy eye or eyes from bacteria, then something has interfered with the fishââ"šÂ¬Ã¢"žÂ¢s ability to ward it off, or there are too many bacteria for it to contend with. Too many bacteria (decaying matter, overfeeding, dead fish, dead snail or crab hidden away), a poor diet (see above reference), ongoing stress (tank too small, tankmate issues, water quality) ââ"šÂ¬Ã¢â‚¬Â something that is letting the bacteria get by your fishââ"šÂ¬Ã¢"žÂ¢s normal defenses ââ"šÂ¬Ã¢â‚¬Â are possible causes. Look into these matters and make corrections. Check your water quality closely (keeping in mind that you cannot test for everything, so something could be wrong that youââ"šÂ¬Ã¢"žÂ¢re not even testing for. For this, you have to play detective.) Make sure you also check for dissolved organics.
