Im guessing he is nipping at your corals? I have one that ate 3 acan frags on me!!!! I heard the best way to get a fish out was with a DIY trap. Take a gatorade or soda bottle that has a mouth that the fish can fit in. Cut the top of the bottle off, invert it and glue it into the bottom of the bottle. Put food in the trap and lay it on the sandbed. Make sure you check on it frequently as Ive heard stories of fish getting trapped and dying because they were left there too long. If you catch the wrong fish, try again lol HTH
Moral of the story, if you put a fish in your tank, that may pick or eat your corals, you need to make sure you have a way of removing it or that you're willing to live with the chance it will eat some of your corals. Something to think about before putting a fish into your tank.