Hermit crabs are interesting, low-maintenance pets. Their name comes from the shells they squeeze into, leaving only their front claws and eyes peeking out at the world. These small crustaceans require a daily diet of fresh food and water, plus a misting of water to keep them moist. Housing is pretty simple, too: A tank with gravel on the bottom will do nicely. Your child will need to be attentive to the hermit crab's behavior, since they do molt regularly and require progressively larger shells to wear as they grow. Hermit crabs are a great way to introduce your child to the world of responsible pet ownership.