i currently have some hawaiin blue band hermits(highly recommend), scarlets, a few blues and some ceriths and nassarius for a CUC also an emerald crab, a sally lightfoot crab, and the usual hitchiker thing in my 20 gallon. My LFS has a sweet looking sea serpent star that just devours leftover food and detrius off the sand bed. Any ideas? experiences? recommendations on something else neat?

Do you have fish or corals in the tank? Sally lightfoot crabs are not reef safe.

both, i got it from a lady who had about 6 in her 150 gallon reef tank and they were doing fine and she had kept them for years in the same reef tank so i think im good with this one. Thanks for the concern though

in such a small tank... that crabs probably gonna eat everything in sight...thats a big space change...and the reason that it wasnt eating everything in the 150 is because there was so much space... also crabs in general do more harm then good in a reef tank... as for the serpent star those guys can grow to be 8inches in diameter (of the oral disc!) and it too will probably eat everything in sight...ESPECIALLY in a 20g...