reef custodians

[ponokareefer]

As others have pointed out, either avoid crabs all together, or only get a couple of smaller hermit crabs. I have a couple of them, but only as something neat to have in the tank, not as a major part of the clean up crew. Also, shrimp can and will steal food from corals. I have some in my tank though, as they just look so awesome, that I can tolerate the stealing.
Snails are one of the best part of a clean up crew in my opinion. Get a good variety, and you should be good to go. The one snail per gallon and a half rule is really high though. I would say maximum for you size of tank should be 50. I only have about 20 in my 125 gallon. Avoid the bumble bee snails though.
Also, a brittle star can do a really good job of cleaning things up. Just avoid the green ones, as they will eat your fish.