Post the pics in the fish disease forum and see if it a disease or an injury before moving them. As you do not want to add stress that is not necassary, it could make problems worse. If you have a fuge, move the emeralds in there for sure. At least that is what I would do. I personally don't trust crabs, or large snails. I think the only things I trust are smallish snails, shrimp, nems, and corals...