There are 4 distinct species of horseshoe crabs, with the most common species found in the reefing hobby hailing from the American Atlantic coasts.  The other 3 species are less commonly available and are native to Southeast Asia.  In the wild, the horseshoe crab generally prefers shallow coastal areas with soft, sandy bottoms where they can forage for food and lay their eggs.  They are adaptable to a wide variety of conditions in home aquaria but a tank with a generous sandbed is highly recommended.

The horseshoe crab is a highly efficient substrate  aerator that will almost constantly be found turning over the sandbed in its search for food.  It also makes for a unique conversation piece in a home aquarium.  It is reef safe and will not bother any invertebrates or corals.  The horseshoe crab’s diet consists mainly of worms and other meaty organisms that it finds while scavenging in the sandbed.  It has also been known to eat algae in smaller quantities.  Many hobbyists will supplement a horseshoe crab’s diet with small pieces of squid.

Horseshoe crabs are well known in the medical industry for their unique blue blood.  This is because their blood does not contain hemoglobin.  Due to this unique trait horseshoe crab blood has a wide variety of medical uses and can sell for $60 000 a gallon in its purified form.