scratching sure isn't a good sign of a heathly fish, and could be ich. Usually by the time you can really tell a fish has ich,(i.e. seeing the white spots) it takes drastic measures to get rid of it. Anyways you should put him in a Q tank for about one month, that is the going rate. Some do it for less. But I would start feeding with garlic, you can find great recipies on this site. If you notice anymore signs you may want to medicate the Q tank.