We had a yellow dottyback that was a terror. It would haze anything its size or smaller we added to the tank no matter what its shape. It would sprint out of the faux cave it made its home, nip a fish, and fly back into the cover of its cave where it would glare at fish menacingly until it would spring again. Ok, so the glaring may
be anthropomorphizing on my part.
We put its cave all the way at one end of the tank so that it would at least have a lot of ground to cover when it sprang for other fish. Eventually it would seem to lose interest in new fish, but they'd take quite a beating for a few weeks beforehand. We never got rid of it because it was one of only 2 fish to make it through 3 moves.
Anyhow, is yours a problem with all fish or only new ones you add to the tank? If you're sure you want to get rid of him, you may want to try a fish trap like this one, Ultralife Fish Trap
. Others could probably tell you how to make one yourself. If you want to catch him without having to break down your tank then a fish trap is probably the answer.
Let us know what you decide to do and how it goes!