is he to far gone already?
< Cichlids , like Oscars are pretty tough customers. Get the nitrates down, service your filter and add some salt to the water to increase the slime coat on the fish. If he is still having problems then he may be suffering from a bacterial attack on his skin and gills. Look at a Furanace type of medication for treatment but watch out. It will probably kill the good bacteria in your filter too.> I usually change 25% of the water once a month, and the same goes with gravel vacuuming.
