oscar fish

i have had an oscar fish for about 18 months.  about a year ago he was in a tank with a shark who got sick and died (spine curved and was unable to swim).  oscar is now by himself in the tank and for the past couple months is having problems swimming.  he will tip over go upside down etc. but no sign of his spine curving like the shark did.  he also has a round hole in his fin on the side that has been there for quite some time but no sign of  infection. he still eats fine.  is there anything i can do to help him swim better or help the hole in his fin? thanks so much

[Crumpet]

I know just what you are talking about. I had a goldfish who had the same problem. From what it sounds like your fish has a bunch of air stuck inside him. I'm not really sure how this happens but a vet told me this when my fish started swimming strange, upside down, sideways etc. They said that usually this happens when you feed your fish flake food and it gulps down the accidentally. This also can happen with other food too, but less likely. Unfortunatly I don't know of a solution. My fish got along ok for quite some time though with this problem. I hope this helps.