To properly care for hermit crabs, place them in a large tank with a layer of substrate in which to bury themselves. Hermit crabs are social, so you should have at least 3-4 animals in each tank. Keep the humidity in the tank at 75-85% and the temperature between 75° and 85°F. You should provide your crabs with extra shells, climbing toys, and places to hide. Place one dish with freshwater and one dish with saltwater in the tank, and feed your hermit crabs a varied diet of seafood, fruits, vegetables, and meats. For tips on keeping your substrate clean, read on!