What is wrong with its eye?

[tara527]

I have a fish that all of a sudden on one of its eyes there is a bubble. I don't know what it is, or if there is anything I can do for him. It was not there yesterday.

 

[tara527]

It is a dansel fish that I have had for 8 months. There are 2 others with him, and several hermit crabs. There has been no agressive behavior amongst them. Nothing new has been added for months. It is a 55 gallon tank. I will test the water and post the result shortly.

 

[tara527]

Here are the water parameters.
Temp 82
salinity 1.023
ph 8.4
Alkalinity low to normal
Nitrite 0
Nitrate between 0 and 2.5

 

[dzones]

not sure if this helps but when i purchased a yellow tang from my lfs the guy kinda dropped the bag when he was tying it. all seemed ok but when i got home the poor guy's eye had like a big bubble. it stayed for about a week then just dissipated to normal and has been for almost 2 months now.
perhaps your fish also received some trauma to the eye area???