Need help with sinking fish

[metalslug]

This fish will swim and then sink like a rock. Hes been like this for a few months. He eats like a monster, and is very aggressive, any ideas how to treat him?

 

[Kitiara]

Looks like some sort of swim bladder problem, does it also seem to have problems staying upright when on the bottom (either falling over, struggling for balance or leaning against things?)

If it is swim bladder there are a number of treatments depending on the cause, and the longer it goes on for the less chance there is of a cure. I recently lost a fish that had swim bladder issues, I treated with everything I could but eventually I think she just gave up and stopped trying any more and lay on the bottom of the tank.