First, do you have a lot of algae for them. I wouldn't want you to get a full cleanup crew and have them starve to death. In conjunction, I know that firefishspike suggested nudibranches. I really wanted one, but I've heard that after they eat all the algae, they tend to starve to death - so keep that in mind. IMO I would wait until you have a good supply of algae, then get a bunch of snails. That's really my entire cleanup crew. One could argue that the shrimp & star help, but that's more for the big pieces of food that are left over. I've read many posts that claim that crab can pick at corals. I'm still thinking of getting a sally lightfoot or two, but I'm trying to do a hermitless tank.
It's ultimately you're tank, so do what you want. I just wanted to add my 2 cents, and let you know what my 75 gallon has in it.
FYI my tank has been up since Feb. and finished it's cycle in mid-March. I added the snails about two weekes ago. (I was waiting for algae.)
Good luck!