If you're looking for a small, attractive crab to brighten your aquarium, the red claw crab fills the bill. This Asian species is also known as the Thai crab. If you're keeping red claw crabs in your aquarium, you must provide an area for them to get out of the water, as they require occasional air.
Because red claw crabs are Houdinis with pincers, keep them in an aquarium with a tight lid. If a crab escapes, find him quickly. Without access to water, he'll die in just a few hours. While you can keep red claw crabs in fresh water, they do better in brackish water. Use sea salt to create a brackish environment, with one teaspoon of salt for every liter of water. Keep the water temperature at approximately 75 degrees Fahrenheit, and never allow it to climb above 85 degrees.
Males and Females
It's safest to keep a lone red claw crab. Males become quite aggressive and territorial. You can try keeping one male together with several females, if you're sure of the crab's sex. Look at the pincers to determine red claw crab gender. Males have larger, more colorful pincers -- a bright red versus the darker red of the females. Don't expect much in the way of offspring. Red claw crabs are difficult to breed in captivity, so your pet probably originated in the wild.
Provide ample places for your crabs to burrow and hide in your aquarium. In nature, they live in holes along riverbanks. Rocks and typical aquarium decorations, such as caves, serve as suitable hiding spots. Show your crabs to their best advantage with light sand in the bottom of the aquarium. Red claw crabs are nocturnal, so they'll hide for much the day. If your tank isn't near a window providing ample natural light, you'll need an ultraviolet reptile or fish light allowing the equivalent of about 10 hours of daylight.
Feeding Red Claw Crabs
Most crab species feast on practically anything, and the red claw crab is no exception. Feed your pets dried fish, dried or frozen bloodworms, shrimp and vegetables such as peas. You also can feed commercial crab food. If you keep your crabs with tropical fish, they might munch on smaller varieties. They'll also chase any fish who swim too close. If you keep live plants in the aquarium, they are potential crab snacks. During their molting period, provide your crabs with calcium supplements.