Hermit crabs. A mysterious animal. They do not grow their own shells, so how do they gain them? Once a hermit crab has finished its' larval stage in the ocean, it emerges onto land, finds its' first shell and tries it on for size. Once finding a good size shell for themselves, they go on about their day. But where do these shells come from? They are none other than the shells of long passed gastropods such as sea whelks or sea snails. Since hermit crabs do NOT grow their own shell it is required to keep a good variety, at least five to six shells per hermit crab in the tank for them to change into. WAIT! Before you go out to buy the biggest shell you can find, measure your hermit crabs' current shells' opening. The new shells' opening should be only a small bit bigger than the current shell. Before buying any shell though, here's a tip: Hermit crabs such as caribbean hermit crabs, also known as purple pinchers, prefer round-opening shells with a mother-of-pearl interior, whilest equadorian hermit crabs, or E crabs, prefer a flatter, more elliptical shaped opening, and usually a rough or non-mother-of-pearl interior. Remember! Painted shells are highly toxic. It's not mainly the paint that does them harm, but the stuff used to /attempt/ to keep it fron chipping. So say no to painted shells, glue-or stick-on googly eyes, or anything of this sort! Your little friend will appreciate it with all of his or her ganglia.