As the hermit crab eats, scraps of food float away which the anemone eats. In turn, the anemone provides protection for the hermit crab. When a crab changes shells, it may even place its anemones on the new crab. Most arthropods are scavengers, eating just about anything and everything that settles to the ocean floor. Skeleton shrimp feed detritus, algae or animals.
Crabs feed on mollusks they crack with their powerful claws.
Their biggest predators are gulls.