Common name: Seven-eleven Crab

General Information

The Seven-eleven Crab or Spotted Reef Crab, scientifically known as Carpilius maculatus, is a strikingly unique species of crab that is easily recognized by its vibrant red spots on a cream or light brown carapace. The name "Seven-eleven Crab" comes from the characteristic seven large spots on the top of its shell and four smaller ones near the edges, resembling the numbers on a pair of dice. This species is native to the Indo-Pacific region and is often found in coral reef habitats.

While not a common addition to home aquariums due to its size and specific care requirements, the Seven-eleven Crab is a fascinating species for advanced hobbyists and public aquariums. Its bold coloration and intriguing behavior make it a captivating subject for observation.

Care

Carpilius maculatus requires a spacious aquarium with plenty of live rock and hiding spaces. These crabs are nocturnal and prefer to remain hidden during the day, emerging at night to forage. They are best suited for species-specific tanks or tanks with robust tank mates, as they may prey on smaller or more delicate species.

Water quality is crucial for their health, with stable parameters and a well-maintained environment being essential. Regular monitoring of ammonia, nitrite, and nitrate levels is recommended to ensure optimal conditions.

Diet and Feeding

The Seven-eleven Crab is an opportunistic carnivore, feeding on a variety of foods in its natural habitat, including mollusks, small fish, and detritus. In captivity, they can be offered a diet of meaty foods such as shrimp, squid, and fish, as well as high-quality pellets or frozen foods designed for carnivorous marine species.

Feeding should be done sparingly, as overfeeding can lead to water quality issues. Providing food every two to three days is generally sufficient, and any uneaten food should be removed promptly.

Behavior and Compatibility

Carpilius maculatus is a solitary and territorial species, often displaying aggression towards other crabs or similarly sized tank mates. They are best kept alone or in very large tanks with ample space to establish their own territory. Their nocturnal nature means they are most active during the night, which can make them less visible during the day.

Due to their predatory tendencies, they are not considered reef-safe and may pose a threat to small fish, invertebrates, and even corals. Careful consideration should be given to tank mates, and they are generally better suited to fish-only systems or dedicated crustacean tanks.

Health and Common Issues

The Seven-eleven Crab is a hardy species when provided with proper care and a stable environment. However, they can be susceptible to shell diseases and stress-related issues if water quality is poor or if they are housed in an inappropriate setup.

When selecting a specimen, look for a crab with a smooth, intact carapace and active behavior. Avoid individuals with visible signs of damage or lethargy. Regular water changes and maintaining a clean tank environment are key to preventing health problems.

Habitat

Carpilius maculatus is naturally found in coral reefs and rocky substrates throughout the Indo-Pacific region, including areas such as the Red Sea, East Africa, and the western Pacific Ocean. They inhabit depths ranging from shallow waters to around 50 meters, often hiding in crevices or under rocks during the day.

In captivity, replicating their natural habitat with plenty of live rock, caves, and overhangs is essential for their well-being. Providing a dimly lit environment or areas of shade can also help accommodate their nocturnal behavior.