Also, I forgot to mention this, in Marine Invertebrates by Ronald L. Shimek he recommends not to get more than 1 hermit crab per 10 gallons if you are doing a reef tank. I've also read that some corals can become damaged from the hermits walking on them. Some people have had great success with large numbers of the hermits though so I don't know what to believe. Something to think about at least.