Zoo Med's All Natural Hermit Crab Sea Sponge have natural minerals from the ocean that is essential to the longevity of your hermit crab. Hermit crabs enjoy drinking water through a sponge rather than an open dish of water. This also helps in preventing accidental drowning of your hermit crab. Also provides beneficial humidity to your Hermit Crab enclosure which is necessary for the long-term health of your Hermit Crab. Shipping weight: 1/10 lb.