Sick Red Oscar

This Red Oscar doesn't seem to have much energy anymore.  We have given him a few goldfish to feed on and there are still some left in the tank as he does not have the energy to "get" them.  He also has not eaten in a few days becuase he can't seem to make it to the top of the tank to get his food.  He is pretty much laying on the bottom of his tank, doesn't move much and when he does swim it is sideways, sometimes almost completely sideways.  I'm not sure what I can do for him since I don't really have any idea what is the matter.  His water and filter were changed recently but he also seems to have a large growth-like bubble on the bottome of his body.

[ChitChatNine]

Hi, I do not have the expertise in this area but wanted to welcome you to the community and wondered how things are going now ?

C~