Catching a rogue crab

[likwid]

So I have had this rogue crab in my tank from the start (8 months ago). It is shaped like an emerald crab, and has a black body with hairy, light orange legs. He only comes out at night, and is extremely quick. As soon as he senses any movement from me inching up to the glass, he runs into a rock crevice and hides. He doesn't seen to be doing any damage in the tank. I have ever seen it nipping at corals, nor has it killed any of my livestock. I have seen him going to town on a clump of algae before though.

I caught a similar crab like this when I first set up my tank buy putting a little glass bowl in the tank, propped it up against a rock, and stuck an algae tablet inside. The next morning that crab was caught in the bowl and I was able to remove him. I was never able to get this one, and now with my tank populated with snails, hermits, and a cleaner shrimp, there is no way I can try this again. As soon as I put an algae tab in the glass bowl a snail gets to it, or my cleaner shrimp dives in, grabs it, and scurries away with it in his hands. Pretty funny to see actually.

Anyways, does anyone have any other ideas for catching a crab like this in a populated tank? Or, should I just leave him in there since he hasn't done any harm?