Common name: Blue Knee Hermit Crab

General Information

The Blue Knee Hermit Crab, scientifically known as Dardanus guttatus, is a fascinating and visually striking addition to marine aquariums. Its reddish-brown legs, adorned with white spots and blue knees, make it a standout among hermit crabs. This species is part of the Diogenidae family and is commonly found in tropical and subtropical waters of the Indo-Pacific region, where it inhabits sandy and rocky substrates.

Hermit crabs like Dardanus guttatus are known for their unique behavior of occupying empty snail shells to protect their soft abdomens. As they grow, they require larger shells, making them an interesting species to observe in captivity. Their active and curious nature adds life and movement to any aquarium setup.

Care

The Blue Knee Hermit Crab is relatively easy to care for, making it suitable for both novice and experienced aquarists. They thrive in aquariums with live rock and sandy substrates, which allow them to forage and explore. Providing a variety of empty shells of different sizes is essential to accommodate their growth and prevent territorial disputes.

This species is highly adaptable and can tolerate a range of water conditions, but stable parameters are crucial for their health. They are excellent scavengers, helping to keep the tank clean by consuming algae, detritus, and leftover food. However, they may occasionally knock over small or unsecured corals while exploring, so caution is advised in reef setups.

Diet and Feeding

In the wild, Dardanus guttatus is an omnivore, feeding on algae, detritus, and small invertebrates. In captivity, they can be fed a varied diet that includes algae wafers, sinking pellets, and meaty foods like chopped shrimp or fish. Supplementing their diet with natural algae growth in the tank ensures they receive balanced nutrition.

Feeding should be done sparingly, as these crabs are efficient scavengers and can find much of their food within the aquarium. Overfeeding can lead to water quality issues, so monitor their intake and adjust portions accordingly.

Behavior and Compatibility

The Blue Knee Hermit Crab is generally peaceful but can exhibit territorial behavior, especially when competing for shells. Providing an ample supply of empty shells can help mitigate conflicts. They are active and inquisitive, often seen climbing rocks and exploring their surroundings.

While they are considered reef-safe with caution, they may occasionally disturb small corals or invertebrates while foraging. They are best kept with other peaceful tank mates and are compatible with most reef-safe fish and invertebrates. Avoid housing them with aggressive species or those that may prey on hermit crabs.

Health and Common Issues

The Blue Knee Hermit Crab is a hardy species, but like all marine invertebrates, it is sensitive to changes in water quality. Maintaining stable salinity, temperature, and pH levels is essential for their well-being. They are also vulnerable during molting, a process where they shed their exoskeleton to grow. During this time, they may hide and should not be disturbed.

When selecting a Blue Knee Hermit Crab, look for active individuals with intact legs and healthy coloration. Avoid crabs that appear lethargic or have damaged appendages. Providing a stress-free environment with plenty of hiding spots and a stable diet will help ensure their longevity.

Habitat

In the wild, Dardanus guttatus is found in tropical and subtropical waters of the Indo-Pacific, including coral reefs, lagoons, and sandy areas. They prefer habitats with ample hiding spots and access to empty shells. Replicating this environment in captivity with live rock, sandy substrates, and a variety of shells will help them feel at home.