How to Feed Sand Crabs

Studying Wild Sand Crabs

Understand how sand crabs behave in the wild. They burrow into the littoral sand where the tide meets the shore, and they scavenge most of their food from what they find buried in the sand. The term "sand crab" describes a variety of large (often predatory) and small (often scavenging) species, and you must suit any feeding regimen to your particular crab. Consider the differences between large and small sand crabs: Larger sand crabs tend to feed on live or decaying prey that they find while burrowing. This prey may include smaller crabs, baby turtles, and the carcasses of dead shorebirds. As larger crabs burrow, they aerate the sand. This helps to keep air and water circulating in their habitats. Smaller sand crabs feed on mollusks, worms, plankton, and algae. They are mostly scavengers: they keep their ecosystem clear of decomposing organic matter, which could host harmful bacteria.

Observe how sand crabs naturally feed. The crabs bury themselves in the sand, facing the ocean, with only their eyes and front antennae exposed. When the tide recedes and washes over them, they unfurl a second set of antennae that filter tiny plankton from the water. The movement happens very quickly. Thus, a sand crab can gather several morsels from each receding wave. Most crabs can move in any direction—forward, backward and sideways—but a sand crab moves only backward. Thus, it must position itself carefully to reap its meals from the waves.

Know the mating habits of sand crabs. In the wild, mating occurs mostly in spring and summer. A female may produce as many as 45,000 eggs. She carries them on her abdomen until the eggs hatch – about 30 days later. For two to four months, the larvae drift as plankton, and currents can carry them far across the sea. Sand crabs can reproduce during their first year of life if the water is warm enough. They don't usually live longer than two to three years.

Keeping Sand Crabs in a Tank

Consider the challenges of removing sand crabs from the wild. They are saltwater shore-dwellers, and they need high temperatures to survive. Sand crabs live in rhythm with the tides, and it can be difficult to replicate the delicate littoral ecosystem in which they thrive. Furthermore, sand crabs feed on such a diverse diet that you may have a hard time giving them the variety they're used to.

Set up a tank with fresh beach sand and seawater. In the wild, sand crabs bury themselves deep in wet sand and catch plankton with their antennae. Replicate this process by filling your crab's habitat with beach sand, then pouring seawater over the sand a few times each day. Use any glass aquarium. Bear in mind that sand crabs cannot dig in sand that is too dry or densely-packed. Try to bring the beach sand directly from the ecosystem where you got the crab. Local beach sand is more likely to contain the insects and microorganisms that your crab needs. Sand crabs naturally gather in shoals, so it should be okay to put several sand crabs in the same tank. Remember, however, that large crabs like to eat smaller crabs.

Regularly refill the tank with seawater. Homemade saltwater will not do; it needs to contain algae and plankton. You can buy plankton, algae, and aquarium-grade seawater at some aquarium-supply and exotic pet stores. Be warned that these supplies can be expensive. Understand that this tactic is a short-term experiment to study the behavior of a sand crab. It is not necessarily a sustainable, long-term way to keep a sand crab as a pet. If you only need to study the sand crab for a short time, consider returning it to the wild when you're done.

Consider getting a hermit crab instead. Sand crabs are difficult—sometimes nearly impossible—to keep as pets. If you are looking for a crab that's easy to raise and feed, consider getting a hermit crab. Do your research, create a habitat, and learn to care for hermit crabs. Aquarium hermit crabs thrive on practically any food, from algae and leftover fish food to beef, eggs, and vegetables. In the wild, hermit crabs have been known to eat leaves, fruit, and even wood. You can also buy commercial hermit crab food that mimics the crab's natural diet.