Gorilla crabs are easy to stab with a chop stick or wooden shish kabob skewer. Go very slowly with the skewer when when you see them. They tend to be curious with the skewer tip. When you get within range, let 'em have it. Then put it between two pieces of graham cracker with melted marshmello and a chocolate square. A gorilla smore!
Pistol shrimps usually make one "crack", it's very loud. Mantis shrimps generally make more than one "click" in succession. I'm still looking for one or two that came in my live rock. I removed two already by ID'ing their hidey hole. I removed the rock, positioned it over a bucket, and poured seltzer water over the rock. They fell out into the bucket. I took them to the lfs where Danny, an employee at the lfs, took them home and is now keeping them in a 12 gallon nano, by themselves. I did capture one very large gorilla crab in a trap. I took it to the lfs and Danny accepted the crab and fed it to the mantis! Oh, the life of captive crabs. They are evil, but mantis shrimps are
demonic! Happy reefing!