Horseshoe Crab

Limulus polyphemus

Identification	Dome-shaped brownish carapace with a long, rigid tail spine. Ten walking legs visible from beneath. Ancient arthropod — not a true crab. One of the oldest species on Earth.
Maximum Length	Up to 24 inches
Origin	Atlantic Coast, Gulf of Mexico
Minimum Tank Size	100 gallons
Reef Compatibility	Generally reef safe

Behavior

Sand-sifting bottom dweller. Plows through fine substrate constantly, turning over and aerating the sand bed. Requires a deep, fine sand bed to function and feed properly.

Diet & Feeding

Carnivore/omnivore. Feeds on worms, mollusks, and organic detritus buried in the sand. Requires supplemental feeding of meaty marine foods placed on the substrate.

Cautions

Grows extremely large — unsuitable for most home aquariums long-term. Needs very deep fine sand substrate. Can overturn decorations and corals placed on sand. Best suited to large FOWLR or species tanks.