I bought this
http://www.jlaquatics.com/phpstore/s...t_ID=am-trap00 to get my koran angel out of my tank that started to eat stuff. Worked wonders, Just put it in and leave it for 2 days, if you have a mag float use that to hold the trap suspended in the tank off the sand bed, and then after 2 days put a bit of frozen food in their so it takes some time to release pieces but releases a bit so the fish can smell it and have to swim in the trap to get some food.
Or for a tang just put a piece of nori in there wrapped around something so it does not come out and the tang should go in their pretty quick.
Hope this helps
Tony