I just came home from work and see a golf ball sized lump on the side of my 2 year old Oscar I don't know what the problem could be... I just did a water change yesterday, I can't really see this being something in the water.. almost looks more towards the rib cage and not the stomach. I'm very concerned, he was my first SA cichlid. Background on the tank... 125g 6 footer, well filtered (just fed them so it's a little cloudy in the pic) with another Oscar, young flowerhorn, and a parrot. He's the king of the tank and nobody messes with him. Maybe he slammed into one of the rock decorations? I'm really confused, he doesn't even look distressed. Please help!