In the wild Horseshoe crabs feed on a number of worms, mullusks and seaweed. They will also eat bits of fish and shrimp that fall to the bottom.

They dig around in the sand and mud to find whatever they can to eat. Basically they are scavengers.

If you are keeping horseshoe crabs in an aquarium, you can feed your horseshoe crab bits of clams, worms, brine shrimp as well as any type of sea food as long as the pieces are small enough for the size horseshoe crab that you have.