Darthodo - That's a pretty clean split you got there, and if it ever was worse, it's already healed pretty well. The tissue looks healthy, it's full, rich in color - which means adequate blood flow, and like I said, the split is pretty clean, not jagged, and the base of the wound seems to have sealed, which is good because it significantly lowers chances of infection. I am guessing that this fin will heal fine, a little unsightly, but for the most part is superficial now. It might take months, and keep in mind that it is not going to fuse as human skin does - reconnecting the tissues from the sides, but rather, is going to grow out from the base to the tip. Make sure you keep your water parameters top notch and for added immunity and tissue regeneration, look into a vitamin-soak for his foods (good idea for all your little buddies).