Did you condition the two of them for a few weeks prior to this? It's important that you do so the female starts to get eggy and wants to breed since the timing would be good.
To help his fins, just clean water should do as well as a high protein diet. If you conditioned him first, this will help him regrow his fins a lot faster too since he has all of those resources to draw upon.
It's best if you watch your breeding pair together very closely for the entire day to make sure. Sometimes things go awry.