Sally Lightfoot Crab

Quick Care Guide

Care Level: Easy to Moderate
Minimum Tank Size: 30 gallons
Temperament: Peaceful to Semi-Aggressive
Diet: Omnivore (primarily algae)
Reef Safe: With caution
Adult Size: Leg span up to about 3 inches
Region: Atlantic and Eastern Pacific
Scientific Name: Percnon gibbesi

Which Sally Lightfoot Crab Is This?

The name Sally Lightfoot is shared by two different crabs. This is Percnon gibbesi, a flat, fully aquatic reef crab also called the Nimble Spray Crab. It is not the large, red shoreline crab (Grapsus grapsus) seen on the rocks of the Galápagos, which is not suited to reef aquariums.

Tank Requirements

Provide plenty of live rock with narrow crevices, since this crab relies on tight hiding places for security. It is quick and agile, so overflow boxes and open plumbing should be covered to keep it from wandering where it does not belong.

Diet and Feeding

Sally Lightfoot Crabs graze hair algae, film algae, and macroalgae, and they will also take leftover meaty foods. When algae runs low, supplement with dried seaweed, algae wafers, or sinking pellets two to three times per week.

A well-fed crab is far less likely to go looking for other food sources in the aquarium.

Temperament and Tankmates

This crab usually ignores larger fish, but as an opportunistic feeder it may catch small shrimp, snails, or very small or sleeping fish. It is best kept with medium-sized, active fish rather than tiny gobies or ornamental shrimp.

Avoid triggerfish, puffers, hawkfish, and large wrasses, which may prey on crabs.

Reef Compatibility

The Sally Lightfoot Crab is considered reef safe with caution. Most individuals leave corals alone, but some pick at zoanthids, soft corals, or other polyps, especially when underfed. Keep an eye on its behavior once it settles in.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Acclimate slowly and maintain stable parameters to support healthy 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

• Feed it when algae runs out: Offer seaweed or pellets so it stays focused on grazing.

• Watch small tankmates: Small shrimp, snails, and tiny fish may be at risk from a hungry crab.

• Cover overflows: This fast crab can slip into overflow boxes and sumps.

• Monitor coral behavior: Remove the crab if it begins picking at polyps.