Keep in mind that for the most part, though, there are two common species that you'll find available- Coenobita clypeatus (purple pincher) andCoenobita compressus (Ecuadorian crab). Although, depending on where you've purchased your crab, you may have one of the more exotic species; Petco and mall kiosks are popular for selling species from the Pacific Rim.
HERMIT CRAB 101 (Identifying your Crab - PPs and Es)
Both land and aquatic species have highly specific habitat requirements, and the latter need an established saltwater aquarium. Beginners would be well advised to opt for terrestrial hermit crabs, as maintaining a marine aquarium requires some expertise. Several species of land hermit crabs appear in the pet trade, all with slightly different requirements, so research the species you wish to keep before setting up their home. Among the most widely available species and the most suitable for beginners are the Caribbean hermit crab (Coenobita clypeatus) and the Ecuadorian (Coenobita compressus). Other land hermit crabs occasionally appear for sale, but they tend to be more delicate.
Land Hermit Crabs - Katharine's Crawling Creatures
Fully aquatic hermit crabs, which are all marine, need a saltwater tank as carefully regulated as that for any other sea creature. While land hermit crabs are not the low maintenance pets some unscrupulous suppliers may claim, marine hermit crabs have more specific needs. However, if you are prepared to invest the time, money and effort, these crabs do make delightful pets.
Land hermit crab | Smithsonian's National Zoo