Sally Lightfoot Crab

Care at a glance

Overview

A fast, active scavenger that spends its day darting over rock and glass grazing algae and picking up detritus and leftover food. Young Sally Lightfoot Crabs are almost entirely herbivorous and pose little risk to tankmates, but as they mature they become more opportunistic and have been known to catch small, slow fish and pick off small or sleeping invertebrates, which is why it earns a caution rating in a mixed reef. It is an accomplished climber and a determined escape artist, so a tight-fitting lid is essential. Feed dried seaweed and occasional meaty foods if algae growth in the tank cannot keep up with its appetite.

In the wild

Native to the tropical Atlantic, from Florida and Bermuda south to Brazil, with a separate population along the eastern Pacific from California to Chile, living among boulders, rubble, and reef crevices in shallow water. It is a fast, flat-bodied crab built for scurrying sideways across rock faces and squeezing into narrow cracks. In the aquarium it wants a large aquascape of rockwork with plenty of nooks to dart into, along with brisk water movement.

Good to know

Percnon gibbesi is currently placed in the family Percnidae, having previously been grouped with the Grapsidae or Plagusiidae before molecular studies split it out into its own family. Its flattened, disc-shaped carapace tops out around 3 cm across, but its long, spiny, spider-like legs give it a much wider reach and a leg span that extends well past that. The legs carry rows of small spines and yellow-ringed joints, and the body shows a mosaic of green, orange, red, and blue markings.

Did you know

It is quick enough to dodge a hand reaching into the tank and will scale glass or rockwork in a blink, a talent that reflects its wild habit of skittering across wave-battered rocks just out of reach of predators.

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