They bite for several reasons
1) they are bored
2) misplaced anger/stress
3) because they can
4) their fins are too heavy and annoy them
If you can figure out why he is bitting, you may be able to stop it.
If he is bored, try moving around decor or adding something new. If he is doing it because he can - there sin;t anything you can do to stop him. Since he is a CT and not a HM or VT, I doubt its cause his fins are too heavy. I have had a few chronic bitters - all heavy finned Halfmoons. I have also had a few VT's bit off their fins because something was upsetting them - once it was the filter, the other did not like divided tanks
Stress coat will help fins regrow if he stops bitting.