Notice the difference between the claws on the "devil" crab and the "gorilla" crab. The gorilla crab has claws that come to a sharp point, tailored for tearing into something and injuring it. The devil crab has a much more flat profile to the claw - more likely for manipulating food to it's mouth. The devil crab actually looks a lot like a porcelain crab, if you ignore the eyes and the dark, eery, color! It's cool enough that you may want to hold on to it for the novelty, unless you hear for certain it is a problem for your tank.