I know I haven't heard of many people keeping barnacles in their reef tanks, but I've had mine for several years and they are pretty interesting. Each barnacle is 3/4"-1" and very busy, constantly skimming the water with their fans. About a week ago, maybe more, I moved one to clean some sand that had blown around it. Well, as it turned out, I accidently pinched off its fan (completely) as I was cleaning it. I figured I had killed it since it had no way to feed. I left it in the tank to see what would happen and, lo and behold, it was actively feeding today with a much bigger fan than it had originally. Do barnacles shed their fans or can they actually regenerate?