Is he pooping ok? If not, try fasting, and epsom salt, bring the temp to mid or high 80's. cut the water current down a bit, just incase he is on his side and cant fight alot of water movement. If hes pooping right, and still eating but floating, do the salt treatment, low water current anyway. A good sign is always appetite, and pooping, just make it as easy for him to rest as possible.