Large tumor... please help!

[apertoolfectcircle]

My brother has been having problems with his flowerhorn. For a while he was having trouble with it being bloated all of the time. He has tried all kinds of stuff to help the fish recover and nothing has seemed to help. Then all of a sudden the fish started growing this tumor-like thing behind it's fin. Please help us identify what this is and if we can treat it...

 

[MoNsTeR FiS]

I would put the fish out of its misery.

 

[Aquanero]

If you have a hospital tank available, cover it with gauze so it doesn't get all over and slice it with a razor so it drains. Treat the tank with kanamycin and methylene blue at one teaspoon per ten gallons of water. DO THIS ONLY IN A HOSPITAL TANK.

This looks like an abcess. This will give it a chance, otherwise it's pretty much done for.