Care guide, husbandry, breeding, disease, sourcing, and tankmate intelligence on Reef Rock Crab - written by the Fast Aquatics editorial team and cross-verified against vendor records on the live marketplace.
Reef Rock Crab (Mithraculus sculptus) is a marine invertebrate kept by aquarists for reef-tank cleanup, biological control of pests, or aesthetic display. Hardy and forgiving of typical beginner mistakes when given proper water chemistry.
Where Reef Rock Crab comes from
Reef Rock Crab (Mithraculus sculptus) is native to Indo-Pacific reef ecosystems, with wild populations distributed across coral reefs, sandy lagoons, and rocky tide pools. Captive specimens are typically wild-collected; some species are starting to be aquacultured but most Reef Rock Crab sold today still comes from wild reef collection. Sustainable sourcing matters - look for vendors who can verify their collection practices, and consider aquacultured alternatives when available.
Reef Rock Crab tank size and setup
Reef Rock Crab requires a minimum of 30 gallons for healthy adults. The minimum is based on the species' adult size (2 inches), territorial range, and behavior pattern. Most Reef Rock Crab sold at small juvenile size will reach full adult size within 12-24 months and the system must be sized to the adult, not the juvenile.
For a Reef Rock Crab setup: mature reef tank with stable parameters, live rock for cover, sandbed substrate (1-2"), reef-grade lighting if photosynthetic, and a fully-cycled biological filter at least 6 weeks old. Newly-cycled tanks under 6 weeks crash the parameters that Reef Rock Crab depends on.
Reef Rock Crab requires standard reef parameters held tightly stable: Temperature: 76-80°F (24-27°C) Specific gravity: 1.025 (refractometer-measured) pH: 8.1-8.4 Alkalinity: 8-9 dKH Calcium: 420-450 ppm Magnesium: 1300-1400 ppm Ammonia + nitrite: Both 0 ppm Nitrate: Under 10 ppm Copper: 0 (lethal to invertebrates)
Reef Rock Crab is sensitive to copper - never medicate the display tank with copper if Reef Rock Crab is present. Stable parameters beat perfect parameters.
What Reef Rock Crab eats
Reef Rock Crab is a algae/omnivore. Provides natural algae control by grazing on filamentous, hair, and turf algae throughout the tank. Supplemental nori sheets and algae wafers ensure adequate nutrition when tank algae is depleted. Avoid copper-based algaecides - they kill Reef Rock Crab. Feed Reef Rock Crab appropriately for its size + activity level. Overfeeding is the #1 cause of water-quality crashes in tanks of all sizes.
Reef Rock Crab tankmates and compatibility
Reef Rock Crab is generally peaceful and compatible with most reef community species. Avoid keeping with predatory fish that view inverts as food: large wrasses (especially halichoeres + thalassoma), triggerfish, pufferfish, and certain large angelfish. Multiple Reef Rock Crab can share a tank but compete for food.
Browse care guides for tankmate-compatibility tables for Reef Rock Crab and similar species.
Reef Rock Crab adult size and lifespan
Reef Rock Crab reaches 2 inches at adulthood with a captive lifespan of 4-7 years with proper care. Many marine inverts molt periodically; provide adequate calcium and a stable parameter regime to support healthy molts.
Can you breed Reef Rock Crab?
Reef Rock Crab breeding in captivity ranges from straightforward (some shrimp, snails) to nearly impossible (most starfish, urchins) due to pelagic larval requirements. Captive-bred specimens are increasingly available from sustainable aquaculture facilities; check with vendors before assuming wild-caught origin.
Common Reef Rock Crab diseases and problems
Reef Rock Crab is sensitive to copper, ammonia spikes, low oxygen, and rapid parameter swings. NEVER use copper medications in a tank with Reef Rock Crab. Symptoms of stress: reclusive behavior, color loss, refusal to feed, abnormal molting (incomplete or stuck molts). Most Reef Rock Crab deaths trace back to acclimation shock or parameter mismatch - drip-acclimate over 45-60 minutes when adding to a new tank.
Where to buy Reef Rock Crab online
Reef Rock Crab is sold at LFS (local fish stores), online retailers, and direct from breeders/wholesalers. Pricing varies widely by source, size, and quality:
Browse live Reef Rock Crab from vetted Fast Aquatics vendors with carrier-tracked overnight shipping (FedEx Priority + UPS Next Day), climate-aware hold logic, and a DOA window (2 hours for fish, 4 for coral and hardy inverts, 24 for plants) with photo-evidence claims. Captive-bred or aquacultured specimens cost more upfront but arrive healthier and integrate faster.
Reef Rock Crab FAQ
What size tank does the Reef Rock Crab need?
Reef Rock Crab requires a minimum of 30 gallons for healthy adults. The minimum is based on the species' adult size (2 inches), territorial range, and behavior pattern. Most Reef Rock Crab sold at small juvenile size will reach full adult size within 12-24 months and the system must be sized to the adult, not the juvenile.
Is the Reef Rock Crab hard to keep?
The Reef Rock Crab needs a tank of at least 30 gallons, a temperature of 76-80°F (24-27°C) and pH 8.1-8.4. Adults reach about 2 inches and live 4-7 years. Best paired with peaceful tankmates of similar size and water-chemistry needs.
What water parameters does the Reef Rock Crab need?
Reef Rock Crab requires standard reef parameters held tightly stable: Temperature: 76-80°F (24-27°C) Specific gravity: 1.025 (refractometer-measured) pH: 8.1-8.4 Alkalinity: 8-9 dKH Calcium: 420-450 ppm Magnesium: 1300-1400 ppm Ammonia + nitrite: Both 0 ppm Nitrate: Under 10 ppm Copper: 0 (lethal to invertebrates) Reef Rock Crab is sensitive to copper - never medicate the display tank with copper if Reef Rock Crab is present.
What does the Reef Rock Crab eat?
Reef Rock Crab is a algae/omnivore. Provides natural algae control by grazing on filamentous, hair, and turf algae throughout the tank. Supplemental nori sheets and algae wafers ensure adequate nutrition when tank algae is depleted. Avoid copper-based algaecides - they kill Reef Rock Crab. Feed Reef Rock Crab appropriately for its size + activity level.
What are good tankmates for the Reef Rock Crab?
Reef Rock Crab is generally peaceful and compatible with most reef community species. Avoid keeping with predatory fish that view inverts as food: large wrasses (especially halichoeres + thalassoma), triggerfish, pufferfish, and certain large angelfish. Multiple Reef Rock Crab can share a tank but compete for food. Browse care guides for tankmate-compatibility tables for Reef Rock Crab and similar species.
How big does the Reef Rock Crab get and how long does it live?
Reef Rock Crab reaches 2 inches at adulthood with a captive lifespan of 4-7 years with proper care. Many marine inverts molt periodically; provide adequate calcium and a stable parameter regime to support healthy molts. The minimum is based on the species' adult size (2 inches), territorial range, and behavior pattern.
What are common problems with the Reef Rock Crab?
Reef Rock Crab is sensitive to copper, ammonia spikes, low oxygen, and rapid parameter swings. NEVER use copper medications in a tank with Reef Rock Crab. Symptoms of stress: reclusive behavior, color loss, refusal to feed, abnormal molting (incomplete or stuck molts). Most Reef Rock Crab deaths trace back to acclimation shock or parameter mismatch - drip-acclimate over 45-60 minutes when adding to a new tank.
Where does the Reef Rock Crab come from in the wild?
Reef Rock Crab (Mithraculus sculptus) is native to Indo-Pacific reef ecosystems, with wild populations distributed across coral reefs, sandy lagoons, and rocky tide pools. Captive specimens are typically wild-collected; some species are starting to be aquacultured but most Reef Rock Crab sold today still comes from wild reef collection. Sustainable sourcing matters - look for vendors who can verify their collection practices, and consider aquacultured alternatives when available.
Related saltwater species you might also keep
Other species in the same category with care profiles on Fast Aquatics. Click any name for the full husbandry breakdown.
Reef Rock Crab taxonomy and care recommendations cross-checked against the following authoritative references and our internal vendor + breeder database.