I have a 15 inch clown knife in a 55 gal. tank. I've had him for about 3 years now. He's always pretty violent when he's eating, and every once in awhile, I'll see a little scratch on his side where he's scraped across the filter tubes. (as a side note, I have two over-the-tank filters, and he has succeessfully slammed into them both so hard that the bottom parts have broken off).

But I digress, the reason I'm writing is because I came home today and his nose is MANGLED. I'm not talking a little scrape. A huge chunk is missing that starts at his nose and stretches back to just over his left eye. I can see blood beneath what's left and what looks like cartilidge. A small portion of his scales are folded over at the top of the wound. I cannot figure out how he did it. There is one flattish rock in there that looked to be on its side, so he may have slammed himself into that.

But I need to know if there is anything I can do. Is there any kind of antibiotic I can put in there so it doesn't get infected? Please, anything you all could offer for advice would be greatly appreciated.

Thanks,
PHIL