Nassarius Snail is a saltwater snail that is used as part of a clean up crew that sifts through the substrate (live sand) looking for bits of detritus. Detritus can be thought of as uneaten foods, fish waste, and any dead or dying organisms. These Nassarius snails do a decent job even though you may not see them very often since they stay submerged in the sand bed most of the time.