Does anyone know what causes it?

My clown fish has a eye that looks like a bubble and swollen

does anyone know what is wrong and how I can cure it?

Cheers

hows your tempreture doing???

I have had that a number of times with my clowns.

You can so anything about pop eye. , best is to leave it and see how it goes. my clown did not eat for two weeks and now she is a box of birds.

I have had the same thing, only on one eye though. I put it down in the end to the clown fish scraping it on the sharp edges of the rocks while being chased.

Dropping the salinity helps also melafix???

Often related to poor water quality, and or insufficient gas exchange at water surface, allowing bacerial infection, or excess nitrogen.

Maybe it got into a fight?

will melafix effect any corals and or invertibrates.

Cheers

apparently anemone's dont take it all that well