Hermit crabs?

[revgeoff]

I am on my third tank and I have always had hermits. Although they can kill off your snails, knock over coarls or steal food from them (larger ones supposedly attack fish but I have never seen or heard of this first hand), I agree with the majority of people and say that their benifits outweigh the problems.
I just think you have to watch out how many you put in your tank. I have heard everything from 1 per gallon (hmmm, 125 of those suckers running around in my tank might be too much)to 1 per 10 gallons.
So I say stock up and if they don't start killing off everything then make sure you tell everyone how cool (or nasty) they are!