One very important element in keeping land hermit crabs alive in captivity is to fill your crabs tank with sand deep enough minimum depth of 3 times the size of their shell and moist enough packs well that your largest crab is able to bury completely to molt successfully. Hermit crabs are natural diggers. They dig to forage for food and also dig when it is time to mold. The deep moist sand protects your crab during the molting process and prevents dehydration which is vital for the longevity of your crab. Unlike the calcium carbonate ìsandî often used in Hermit Crab enclosures, Flukerís Premium Mix for Hermit Crabs, is a perfect blend of all natural silica sand, coconut fiber, sea salt and probiotic. The silica sand packs well and the coconut fiber helps with water retention. Calcium and sea salt are added to replicate the exact sand the Hermit Crabs find in their natural environment. Finally, probiotic has been introduced to help maintain a clean environment.