We have tried everything to get a black and white striped Damsel out of my friends tank. He has killed hundreds of dollars worth of fish with his constant nipping and harrasment.
She can't net him because he knows the net is for him and hides behind the reef. She's tried a fish trap, but can't sit for hours waiting for him to decide it's not a trick. He's very leary of it. Last week she didn't feed the tank for 2 days and then we went fishing with hook and line with a bit of shrimp. He was the only fish in the tank that didn't go directly for the hook. At any opportunity her other fish would take out after it and we'd have to yank the hook from the tank, quickly!!! When he did act like he was going to go for it he would stop short and stare at it. He was teasing us!!!
We're going to try one last thing short of tearing down the reef and really going after him with the net. We put the fish trap in with some brine shrimp in a net inside and no door. When we finally see him in there after however long it takes him to decide it OK, (Probably weeks), then were going to set the trap and try to nab him.