The bone supporting the long trailing dorsal fin on one of my longfin bannerfish (heniochus acuminatus) has broken, and it looks like a clean break. The fin is still there, supported only by the flesh of the fin–I don’t believe there is any (at least not much) muscle in the banner portion of the fin itself. I’ve had fins like this break before, but near the tip. This break occurred only about 1-1.5 cm from the fin’s base. The fish is eating and swimming fine. Should I leave her be? The fin can’t possibly heal the way it is, but maybe it will break off on its own (or get nipped off…) and then regrow? Or does the fish need “surgery?” (I hope not…) Currently the four bannerfish including the one with the damaged fin are being housed in my 125 gallon aquarium and are about 2.5-3.5 in. long not including the banner fins. I do have a qt tank but it’s housing three small fish while I overhaul my 40 gallon tank.

thanks!!!
Update: the fish’s broken fin is still attached by the skin as of now and hasn’t broken off on its own. The fish is still eating fine and I don’t want to stress it further, as all four bannerfish are showing a light case of ich…so I’m making sure they are well fed and get their vitamins and garlic.