Hey, shift9K, did you get your nutrients under control? I'd get the water in top shape before adding more CUC. If later you get the water better, you'll end up with starving snails and crabs.
I have a few hermits in my tank. I only wanted some for the entertainment factor. I read somewhere the other day that one per 10g will be reef safe. I only have 6 in my 125g tank
Right now, they can't move fast enough to get to the food when everyone else is feeding, so they really only do get the leftovers. Many reefers have a snail-only CUC, from what I've read.