Arrow Crab
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Quick Care Guide
Care Level: Easy
Minimum Tank Size: 30 gallons
Temperament: Semi-Aggressive (predatory)
Diet: Carnivorous Scavenger
Reef Safe: With caution
Adult Size: Leg span up to about 6 inches
Region: Caribbean and Western Atlantic
Scientific Name: Stenorhynchus seticornis
Tank Requirements
Arrow crabs need plenty of rockwork to climb, with open areas where they can move their long, thin legs freely. Larger aquariums with abundant live rock provide more natural foraging and help reduce predation on tankmates.
Diet and Feeding
Arrow crabs are best known for hunting bristleworms, but they also scavenge leftover food. Target-feed mysis, chopped seafood, or sinking pellets three to four times per week. A well-fed arrow crab is much less likely to go after tankmates.
Temperament and Tankmates
Keep only one arrow crab per tank, since they fight with each other. Feather dusters, small ornamental shrimp, nudibranchs, and small or slow fish are at risk.
Arrow crabs do well with medium to large, active fish such as tangs, angelfish, and larger wrasses. Avoid triggerfish, puffers, and hawkfish, which may prey on them.
Reef Compatibility
The Arrow Crab is reef safe with caution. It generally ignores stony corals, but a hungry crab may pick at soft coral polyps or small invertebrates.
Water Parameters
Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH
Acclimate slowly and keep conditions stable to support molting. Invertebrates are highly sensitive to copper, and copper-treated water or medications should never be added to an aquarium that houses them.
Common Considerations
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One per tank: Arrow crabs are territorial toward their own kind.
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Not for feather duster tanks: They are well known to eat feather duster worms.
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Feed it regularly: Consistent feeding keeps predatory behavior in check.
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Great bristleworm control: Useful in systems with large bristleworm populations.