Common name: Conical Spider Crab

General Information

The Conical Spider Crab (Xenocarcinus conicus) is a fascinating and unique addition to marine aquariums, known for its slender, elongated body and its habit of decorating itself with pieces of coral, algae, or sponges. This behavior not only provides camouflage but also makes it a visually intriguing species for hobbyists. Native to the Indo-Pacific region, this crab is often found in association with soft corals and gorgonians, blending seamlessly into its surroundings.

This species is relatively rare in the aquarium trade but is highly sought after by enthusiasts who appreciate its unusual appearance and symbiotic tendencies. Its delicate and spindly legs, combined with its conical carapace, give it an almost alien-like appearance, making it a standout addition to any marine tank.

Care

The Conical Spider Crab requires a well-established aquarium with plenty of live rock and coral structures. It thrives in tanks that mimic its natural reef environment, with moderate water flow and stable parameters. Due to its small size and delicate nature, it is best suited for nano or species-specific tanks where it can be observed without competition or predation from larger tank mates.

This crab is nocturnal and spends much of its time hiding or camouflaging itself during the day. Providing ample hiding spots and a variety of coral and algae for decoration will help it feel secure and display its natural behaviors.

Diet and Feeding

In the wild, Xenocarcinus conicus is an opportunistic feeder, consuming detritus, algae, and small invertebrates. In captivity, it can be fed a diet of finely chopped seafood, algae wafers, and frozen foods such as mysis shrimp. Supplementing its diet with marine algae will help mimic its natural feeding habits and ensure its nutritional needs are met.

Feed this crab sparingly, as overfeeding can lead to water quality issues. Offering food every other day is generally sufficient, and it will also forage on its own within the tank.

Behavior and Compatibility

The Conical Spider Crab is peaceful and non-aggressive, making it suitable for community tanks with other small, non-aggressive species. However, it should not be housed with large or predatory fish that may view it as a snack. Its tendency to decorate itself with coral and algae means it may inadvertently damage delicate corals, so caution is advised when keeping it in reef tanks.

This crab is solitary by nature and does not require companions. It is best kept singly or in pairs in larger tanks to avoid territorial disputes.

Symbiosis

One of the most interesting aspects of Xenocarcinus conicus is its symbiotic relationship with soft corals and gorgonians. It often resides among the branches of these corals, using them for camouflage and protection. In return, the crab helps keep the coral clean by removing detritus and algae. This mutualistic relationship is a fascinating example of the interconnectedness of reef ecosystems.

Health and Common Issues

The Conical Spider Crab is relatively hardy but requires stable water conditions to thrive. Sudden changes in water parameters can stress the crab and lead to health issues. Regular monitoring of water quality and maintaining a clean, stable environment are essential for its well-being.

When selecting a Conical Spider Crab, look for active individuals with intact limbs and a healthy appetite. Avoid crabs that appear lethargic or have visible signs of damage.

Habitat

In the wild, Xenocarcinus conicus is found in the Indo-Pacific region, often inhabiting coral reefs and lagoons at depths of up to 30 meters. It prefers areas with abundant soft corals and gorgonians, where it can blend into its surroundings and find food. Replicating this environment in captivity will help the crab feel at home and display its natural behaviors.