Pitho Crab

The Pitho Crab (Pitho mirabilis) is a powerful, highly effective algae-eating crab that makes an outstanding addition to reef and marine aquariums. A member of the Mithracidae family — the same group that includes the popular Mithraculus sculptus (Emerald Crab) — the Pitho Crab shares a similar body style but offers even greater activity levels and slightly larger adult size. Hardy, adaptable, and full of personality, this species is quickly becoming a favourite among hobbyists looking for a natural solution to nuisance algae.

Well known for its exceptional grazing ability, the Pitho Crab eagerly consumes hair algae, bubble algae (Valonia), turf algae, and more complex macroalgae species such as Caulerpa, Bryopsis and Dictyota. Per specimen, many aquarists find them even more effective at bubble algae removal than Emerald Crabs. In addition to nuisance algae, they readily accept supplemental foods and absolutely love sheets of Nori seaweed, making them easy to maintain even in cleaner systems where natural algae growth may be limited.

Pitho Crabs grow up to approximately 4cm across the carapace. Males and females differ noticeably in appearance. Females closely resemble Emerald Crabs and possess large claws that can span nearly twice the width of their body, primarily used for defence. Males, by contrast, have smaller claws and rely more on camouflage for protection. Despite these differences, both sexes are generally non-aggressive and integrate well into peaceful reef communities. As with most crabs, occasional opportunistic behaviour can occur, so routine observation is recommended.

These crabs thrive in mature aquariums with established live rock, which provides ample grazing surfaces and secure hiding places. They adapt well to a wide range of tank sizes and are hardy once acclimated.

Beyond their utility, Pitho Crabs are surprisingly personable. When regularly fed, they quickly learn to associate activity outside the aquarium with feeding time and may approach the glass, waving their claws in anticipation. Their colouration is variable, adding natural visual interest to your clean-up crew.

Abundant in the wild and well suited to captive life, the Pitho Crab is an ideal choice for reef aquarists seeking an effective, reef-safe algae grazer with character. Whether you’re battling bubble algae or simply looking to strengthen your clean-up crew, Pitho mirabilis is a hardworking and engaging addition to your marine aquarium.