Arrow Crab

Arrow Crab requires a minimum of 30 gallons for healthy adults. The minimum is based on the species' adult size (6 inches (legs)), territorial range, and behavior pattern. Most Arrow 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.

The Arrow Crab is rated intermediate difficulty on this care sheet. It 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 6 inches (legs) and live 5-8 years. Arrow Crab (Stenorhynchus seticornis) is a intermediate-care saltwater species that thrives in tanks of 30 gallons or larger with stable parameters.

Arrow 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) Arrow Crab is sensitive to copper - never medicate the display tank with copper if Arrow Crab is present.

Arrow Crab is a carnivore. Eats meaty foods - frozen mysis shrimp, brine shrimp, finely chopped seafood, and quality carnivore pellets. Live food (PE Mysis, live brine, live blackworms) triggers feeding response in stressed or new arrivals. Feed 2-3 times weekly for adults; daily for growing juveniles. Feed Arrow Crab appropriately for its size + activity level.

Arrow 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 Arrow Crab can share a tank but compete for food. Browse care guides for tankmate-compatibility tables for Arrow Crab and similar species.

Arrow Crab reaches 6 inches (legs) at adulthood with a captive lifespan of 5-8 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 (6 inches (legs)), territorial range, and behavior pattern.

Arrow Crab is sensitive to copper, ammonia spikes, low oxygen, and rapid parameter swings. NEVER use copper medications in a tank with Arrow Crab. Symptoms of stress: reclusive behavior, color loss, refusal to feed, abnormal molting (incomplete or stuck molts). Most Arrow Crab deaths trace back to acclimation shock or parameter mismatch - drip-acclimate over 45-60 minutes when adding to a new tank.

Arrow Crab (Stenorhynchus seticornis) 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 Arrow 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.