coke bottle trap....easy to make and works every time....
Get a 1 liter plastic bottle of Coke, the hourglass shaped one. After the bottle is empty ( I recommend rum to help empty it :-D ) rinse it out well and remove the label. Then use a utility knife to cut the top off the bottle, about 3/4 of the way up, or about 1/2 inch above where the bottle is at its widest before it begins to narrow into the hourglass shape. Poke a few small holes in the lower part of the bottle. Then put a cube of frozen food in the lower part, and insert the top part inverted into the lower part so that the opening you drink out of is facing the bottom of the bottle. Put this in your tank and wait. (usually overnight) It works like a lobster trap, he'll go in after the food, but he won't be able to get back out. this simple, cheap trap has always worked for me. It will also work with those nasty little hairy hitchiker crabs that came on your LR you are not too sure if you want in your tank. I have even used it to catch damsels....they can get back out, so it requires your atttendance to be successful catching damsels.
MikeS