As a member, allow me to add a few words...
Though the namesake of the society suggests that all crabs are evil, it aint the initial intention of Witty... it was all done in good fun... of coz there are the hermits and emeralds that does a great job in the reef tank, but I tink the emphasis is on the devious ones that attacks your little fishes and chew on your SPS corals...
Cheers!
