These are often sold as part of the clean-up crew packages for reef tanks, and are indeed interesting additions to most tanks; they are always active and picking off of something. However, there are reports of them bothering weakened corals at some times and even attacking other hermits and pulling turbo snails out of their shells, so use with caution. They do make good detritus-cleaners, but I've found personally that the red-legged hermits, C. diguti, seem to be a little more peaceful.