Description
Sally Lightfoot Crab – Grapsus grapsus
Grapsus grapsus, commonly known as the Sally Lightfoot Crab, is a fast-moving and visually distinctive reef crab best known for its flattened body, long legs, and agile behavior. This species displays a mottled pattern of brown, red, and gray tones that provide excellent camouflage against reef rockwork. Constantly on the move, Sally Lightfoot Crabs are active scavengers that patrol rocks and crevices in search of algae and leftover food, adding both utility and animation to the aquarium.
Origin: Maldives (Indian Ocean)
Depth: Intertidal to shallow reef zones (0–10 m / 0–33 ft)
Lighting: Not demanding; comfortable under standard reef lighting
Flow: Moderate; prefers areas with good water movement and exposed rock surfaces
Tank Placement: Rockwork and substrate; frequently seen climbing vertical surfaces and hiding in crevices
Temperature: 74–80°F (23–27°C)
Salinity: 1.023–1.026 SG
pH: 8.1–8.4
Diet: Omnivorous scavenger – consumes algae, detritus, leftover fish food, and small meaty items; supplemental feeding recommended in low-algae systems
Temperament: Semi-aggressive; generally peaceful when small but may become opportunistic or aggressive as it grows, especially toward small fish or invertebrates
Size: Up to 7.5 cm (3 inches)
Care Level: Intermediate – hardy but best suited for experienced aquarists who can monitor behavior as the crab matures
Compatibility: Reef-safe with caution; suitable for fish-only or robust reef systems; may prey on small fish, snails, or shrimp if underfed or fully grown
