This mantis shrimp hitchhiked on my TBS live rock. It is now living in a 10Gal and my daughter has named it "Smashy". Pretty cool creature... I've been feeding the gorilla crabs to it as well as chunks of LRS. Smashy seems to only go after crustaceans and has been living with a small hitchhiker tiger goby ("Lucky") for a few months now. If it wouldn't bother the porcelain crabs (which I bet it would) I'd probably return it to the main display. For now "Smashy" is doing great and expert at disposing of all the pest crabs I can catch