You should buy a wide variety of unpainted gastropod shells that your hermit crabs can wear. This includes shells of different type, size, shape and mass. You can even buy multiple copies of the same shell to reduce the likelihood of hermit crabs fighting each other for the same shell. Hermit crabs may change into smaller shells if they feel more comfortable in them. Different species of hermit crabs tend to prefer different types of shells. For example, C. variabilis, C. clypeatus and C. compressus love Phasianella, Turbo and Nerita shells respectively.
What shells should I avoid?
Be careful when choosing shells for your hermit crabs. Do not assume that any gastropod shell up for sale is an ideal piece of clothing for your hermit crabs. Do not buy:
Painted shells, since they are a waste of money and are a health hazard to your hermit crabs. The paint may stick to hermit crabs and trap them inside their shells.
Shells with holes or broken parts in them, since they will cause the hermit crab's shell water to leak.
Angaria shells, shells with a long spear protruding out to the side or bivalve shells.
How do I encourage a hermit crab to change shells?
Hermit crabs cannot be forced to change shells unless they are tortured. They would rather let you rip their limbs off than to give up the shell they are wearing, even if they do not feel comfortable in it. However, some hermit crabs are attracted to shells that were previously worn by another hermit crab. You can trick them into thinking that the shells were previously used by rinsing the shells in salt water. If your hermit crab insists wearing a shell far too small for it, try offering slightly larger versions of the same type of shell.
How do I remove the paint from painted shells?
Try boiling the shells in hot water and then peeling the paint off with your fingernails or tweezers. Otherwise, you can try nail polish remover, but make sure that you wash the shell thoroughly afterwards to remove the bad odours. If you still cannot remove the paint, then you will have to throw it out.