Thats how I caught one. I spent 18.99 on a trap and they aren't interested, but I saw one hunting down a crab and to make a long story short we pulled the rock and after pulling it out it jumped into the bucket we had underneath it. So now I am trying to bait them (I think there are two more, one on each end of the tank) into smaller rocks that can be easily taken out w/o destroying my rockwork (the rock they are in are about 30+lb's each and both on the bottom). Cool, what kind of tank is it going to be?