clear blister like bubble on fish

[DaveG99]

I have a tang that has a clear bubble on top of its head. Its about the size of its eye. It almost looks like a blister from a burn. Its been there for a few days. Does anyone know what kind of problem this is?

 

[MegaPods]

Pop eye maby

 

[DaveG99]

its not on his eye. Its above his eye on his head. And it has shrunk and is very small now. Hopefully it will go away completely.