I have been using the clean up crew from garf.org and have been very happy with it. Mine includes the Mexican Red Leg Hermit Crabs (Clibanarius digueti), Cerith Snail (Cerithium strercusmuscarum), and the Nerite Snail (Nerita funiculata). I have been really happy with this crew so far but I am also tagging along to see what others are using since I am in the market for a new crew in the next couple of days. I have never seen my hermit crabs bothering SPS but they do upset my zoos, mushrooms, and other softies at feeding time. They are always trying to take food right out of their mouths. They are not terribly aggressive towards snails and I have actually never seen one of these crabs attack a snail for its shell. I do however see a few walking around in their shells and yes I do have extra shells lying around for the crabs to move into. With that said they could be just moving into the shells of snails that have died off. My tank has been very clean with this crew and I have never had an algae break out other than bubble algae since I set my tank up 8 months ago. If you do decide to go with hermit crabs I would recommend these ones but you may want to skip the hermits all together depending on other people’s experiences. Hopefully we will hear from some of them…