Pitho Crab

Pitho Crabs are highly useful additions to saltwater aquarium clean up crews due to their strong appetite for nuisance algae and their ability to graze in areas that many snails may ignore. Often compared to Emerald Crabs, Pitho Crabs are valued for consuming hair algae, turf algae, bubble algae, Caulerpa, Dictyota, and other problem algae growth on live rock and hard surfaces. Their compact size, cryptic coloration, and steady grazing behavior make them especially useful in established reef aquariums with active algae growth. While they are generally peaceful, they should still be considered reef safe with caution, as they are opportunistic crabs and may occasionally investigate soft corals, weakened invertebrates, or leftover meaty foods.

Introduction to Pitho Crab (Bubble Algae Grazer & Reef Cleanup Crew Specialist)

Pitho Crabs (Pitho mirabilis) are small Caribbean algae-grazing crabs from the Mithracidae family, the same general family group that includes Emerald Crabs and Ruby Mithrax Crabs. In the wild, they are found among rockwork, rubble, and algae-covered surfaces where their mottled coloration helps them blend into their surroundings. In the aquarium, they spend much of their time slowly moving across rockwork and horizontal surfaces while picking at nuisance algae.

Pitho Crabs are especially popular for aquariums dealing with bubble algae or persistent turf-style algae. They are often considered a more reef-friendly alternative to some Emerald Crabs, though individual behavior can still vary.

Care Requirements

Care Level: Easy – Hardy when kept in stable, established aquariums
Minimum Tank Size: 15+ gallons
Aquarium Setup: Requires live rock, grazing surfaces, hiding places, stable parameters, and peaceful tankmates

Pitho Crabs do best in mature saltwater aquariums with plenty of rockwork and natural algae growth. They are relatively small, but they need enough grazing area to support their feeding behavior. They may hide more when kept with aggressive or overly active tankmates, which can reduce how much grazing they do.

Diet & Nutrition

Pitho Crabs are primarily algae-grazing omnivores that feed on nuisance algae, macroalgae, detritus, and leftover foods.

Diet: Omnivorous Grazer – Prefers nuisance algae, macroalgae, detritus, and small meaty leftovers
Recommended Foods:
Naturally occurring hair algae and turf algae
Bubble algae, including Valonia-type algae
Caulerpa and Dictyota macroalgae
Detritus and leftover fish food
Dried seaweed or nori
Algae wafers
Small meaty foods such as mysis shrimp or finely chopped seafood if natural food is limited

Pitho Crabs are best used in aquariums with active algae growth. If the tank becomes too clean, supplemental feeding may be needed to prevent them from becoming overly opportunistic.

Lifespan & Growth Rate

Lifespan: 1-3+ years with proper care
Growth Rate: Moderate – Females can reach around 1.5 inches across the carapace, with males usually staying slightly smaller

Pitho Crabs stay manageable compared to many larger marine crabs, but they are still strong enough to move through rockwork and investigate crevices while feeding. Like other crabs, they molt as they grow and require stable water parameters to molt successfully.

Temperament & Compatibility

Temperament: Peaceful to Semi-Peaceful – Generally non-aggressive, but opportunistic
Reef Safe? With caution – Useful in reef aquariums, but may occasionally pick at soft corals or small weakened invertebrates

Pitho Crabs are generally suitable for peaceful reef aquariums and can be kept with most reef-safe fish and invertebrates. They should not be housed with aggressive crab predators such as triggers, puffers, hawkfish, large wrasses, large crabs, or fish that may pick at small crustaceans. Keeping them well fed and providing natural algae growth may help reduce opportunistic behavior.

Common Challenges & Considerations

Reef Safe With Caution: Pitho Crabs are usually well behaved, but they may occasionally pick at soft corals or investigate weakened animals.
Best for Algae-Rich Systems: They are most useful in aquariums with bubble algae, hair algae, turf algae, or macroalgae growth.
Individual Behavior Can Vary: Like Emerald Crabs, some individuals may be more opportunistic than others.
May Hide Around Aggressive Fish: If housed with intimidating tankmates, they may stay hidden and graze less effectively.
Molting Sensitivity: Sudden changes in salinity, pH, or alkalinity can cause stress during molting.
Sensitive to Copper: Like all marine crabs, they should never be exposed to copper-based medications.

To prevent issues, acclimate them carefully, keep them with peaceful tankmates, provide a mature aquarium with natural algae growth, avoid copper exposure, and offer supplemental foods if algae becomes limited.

Water Conditions

Temperature: 72-78°F
dKH Alkalinity: 8-12
pH: 8.1-8.4
Specific Gravity: 1.023-1.025