For critters, go to J&L, they have the best price and always have them in stock:
http://www.jlaquatics.com/static/livestock/janitors.htm
From my experience, red leg hermits aren't reef safe. They were jacking shells off my snails and grew way too fast. IMO blue leg hermits and red scarlet hermits look safer to me, their legs and claws look more flimsy. But then again, they're crabs, don't expect any of them to be 100% reef safe. Another thing I noticed was when the red leg hermits got together. They go crazy and start messing with the snails, at least mine did.
BTW, I don't think hermits eat aptasia.