We have 4 hermits (2 blue leg, a Halloween hermit, and an unspecified little guy that came in our tank), peppermint shrimp, cleaner shrimp, and a coral
Banded shrimp. We have an emerald
Crab and a variety of snails (Turbo, turban, cerith, nassarius, and nerite snails). Not a bunch of any of them but a few in a 75 gallon display tank and 30 gallom sump. They are cool little buggers to watch. Plus an unknown number of bristles worms, stomatellas, and a really cool flatworm that we've only seen once that came in our live rock. We also have a gazillion starfish and tiny brittle stars that clean. You don't need them per say but they are really fun to watch. Our hermits are HILARIOUS! We have one that changes it's shells almost daily. Literally there is a pile of 4 shells in the back bunched together and he goes and changes his clothes.