Sorry to hear that your fish is unhappy. I'm certainly no expert at this but I know how horrible it is to have a fish who seems ill and not knowing what to do for it. My immediate reaction would be to check your water quality, if you dont have any test kits you can pick one up in most pet shops for little money. If when you've checked your water and it is within the normal parameters then it may be a disease isolated to that particular fish. I have a few diagnositic charts which i looked at to see if the symptoms you spoke of were listed. The only thing I could see that was close was 'Red streaks - red blood streaks or blotches on fins or body'. The chart suggests using 'fungus clear'. I'm not sure about medicating tanks/fish as last time I tried it for swim bladder it really messed up my biological filter and my tank is still cycling now some 3 weeks after the treatment.
Usually if any of my fish are off colour I add aquarium salts, also try feeding him some live blood worms (not too many) as fish love them, they're like treat food. It usually perks mine up and they seem fine the next day.
Hope your fish feels better soon, let me know how you get on. Like I said I'm certainly no expert, being fairly new to this myself, but these are some of the things I'd try first if I were you.
Good luck.
