Mithraculus sculptus - a member of the cleaning crew

Mithraculus sculptus – also known as Mitrax, is a popular crab in marine aquariums due to its attractive appearance and beneficial habits. This small crustacean, reaching a maximum length of 6 cm, is known for its intense green color, which provides excellent camouflage among coral reefs and rocks. This makes it difficult to spot, adding excitement to the observation of its behavior for aquarists.

This crab originates from the tropical western Atlantic, including areas such as the Caribbean Sea, the Gulf of Mexico, and southern Florida. It prefers areas rich in algae-covered rocks and coral rubble. Mithraculus sculptus has a flat, shiny green shell and hairy, dark green legs. Its claws help it feed on various forms of algae, including Valonia. This makes it a common addition to aquariums as a natural ‘cleaner,’ part of the cleaning crew that helps maintain tank cleanliness by consuming excess algae and detritus.

It requires specific water conditions:

• Temperature: The optimal water temperature is between 24°C and 28°C.
• pH: Ranging from 8.1 to 8.4.
• Carbonate Hardness (KH): 8 to 12 dKH.
• Salinity: 1.023 to 1.025 SG.
• Tank size: Approximately 100 liters of water per crab. They need plenty of space as they can become territorial in crowded conditions.

Mithrax sculptus is a rather solitary creature, preferring to live in isolation. In aquariums, these crabs may exhibit territorial behaviors, especially if kept in too small tanks or with other individuals of the same species. This crab is also a nocturnal creature, meaning most of its activity occurs in the evening and night. This makes its behavior more challenging to observe but also more fascinating for patient observers.

Like other crustaceans, the Mitrax crab undergoes molting, during which it sheds its old shell to make room for a new, larger one. This process can surprise inexperienced aquarists, who might mistake the shed shell for a dead crab. After molting, the crab is particularly vulnerable and requires a calm environment for the new shell to fully harden.

Breeding Mitrax in captivity is difficult. Females carry several hundred eggs under their abdomen, but unfortunately, the survival rate of larvae in captivity is generally low. These crabs are susceptible to typical marine invertebrate diseases, such as shell diseases. They are sensitive to copper-based treatments, which should be avoided as they can be fatal.

Although Mithraculus sculptus is generally considered reef-safe, it can become aggressive, especially when food is scarce, potentially harming other aquarium inhabitants. They are compatible with many reef species, but should be monitored to ensure they do not prey on smaller or slower organisms in the tank.

The crab offers both visual appeal and practical benefits in maintaining cleanliness and health in a marine aquarium. However, it requires careful management and an understanding of its natural behaviors to ensure harmony in the tank environment.

Due to its characteristics, the Mithraculus sculptus crab is a valued addition to the so-called ‘cleaning crew’ in marine aquariums. However, like any creature, it requires appropriate living conditions, including proper water quality and stable water parameters. It is important to provide it with sufficient natural food, as otherwise, it may start damaging corals in search of food.

In summary, the Mitrax crab is not only a useful helper in maintaining aquarium cleanliness but also an interesting subject of observation. Its unique behaviors and role in the coral reef ecosystem make it a species worthy of attention for any marine aquarist.