Fiddler Crabs - There are actually over
90 species and subspecies of Fiddler crabs.
Males have only one large claw while
females have small claws. The largest fiddler
crabs only reach a mature size of about 2 inches
across their body. Fiddler crabs can be
found on ocean beaches and retreat to
muddy burrows as the tide goes out (so are
exposed to water that ranges from brackish to
salt water). Other species are found in brackish
water swamps. They are scavengers that feed on
organic matter they find on the surface of rocks
and in the mud. Fiddler crabs found in pet
stores are most likely semi-terrestrial brackish
crabs, which means they need some salt in their
water as well as access to air and dry land.
This can be quite hard to set up in your tank.Hermit crabs - Hermit crabs make interesting, easy care companions. They have their own distinct personalities, are active and curious, and their unique characteristics and low maintenance requirements make them good pets. Hermit crabs are not "true crabs." They have a smaller, soft abdomen which they protect by living in an empty snail shell. They must find larger shells as they grow, and owners of these pets must provide progressively larger shells as their pets grow. In the wild they are omnivores, feeding on both plant and animal material. There are both marine and land hermit crabs. They are probably easier to care for than Fiddler crabs.
A medium size aquarium is
suitable for any sort of crab. You need a lid to
keep in the humidity.