how to catch a crab....

[outtafocus]

I have read that you can use a pop bottle, cut off the neck portion then invert it back into the bottle. Make sure the opening in the top is big enough for your target to slip through. Submerge this bottle trap in the tank with a piece of shrimp or something inside. The crab will go in to get the shrimp and find that he cant climb back out of the inverted top.
Sorry I cant figure how to describe it any better. Pm me if it doesnt make sense.
It may take a few nights or weeks but you should eventually catch the bugger. If you catch him, check to see what kind of crab it is. No point flushing a reef safe crab.