Sally lightfoot crab (Percnon gibbesi) care guide

Group
Other invertebrates
Other names
Nimble spray crab, Urchin crab, Acanthopus gibbesi, Plagusia delaunayi
Family
Percnidae
Origin
Atlantic coasts from Florida to Brazil and Madeira to the Gulf of Guinea; eastern Pacific from California to Chile; invasive in the Mediterranean
Water
saltwater
Maximum size
7.6 cm
Temperature
22–26°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.025
Care level
beginner
Temperament
semi_aggressive
Reef safe
with_caution

Care

The Sally lightfoot crab sold for reef tanks is Percnon gibbesi: a very flat crab with a brown body and long, spiny legs ringed with yellow to orange at the joints. Its carapace is about 3 cm wide; with legs it spans up to about 7.6 cm. The name 'Sally lightfoot' is also used for the semi-terrestrial Grapsus grapsus, which is a different and much more aggressive crab. It is placed in the family Percnidae (sometimes Plagusiidae; LiveAquaria lists Grapsidae). Its flat body lets it slip into narrow rock crevices. Keep it in a large tank with plenty of rockwork for hiding and foraging; it likes strong current and stays in the water more than its shore-crab relatives. Water: 22–26 °C, pH 8.1–8.4, dKH 8–12, SG 1.023–1.025, with calcium, magnesium and iodine for moulting. Clean-up role: it grazes algae, including hair algae and some bubble algae, and scavenges detritus. In the wild it is strictly herbivorous, but in aquaria larger individuals can turn predatory. Since 1999 it has spread around the Mediterranean and is described as the most invasive decapod to enter that sea. Never release this animal or empty its tank water into drains or waterways. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and check the label of any treatment or fertiliser before use. Sources: LiveAquaria (liveaquaria.com/products/sally-lightfoot-crab); Wikipedia (en.wikipedia.org/wiki/Percnongibbesi). Checked October 2026.

Diet

Mainly herbivorous: grazes algae on the rockwork. Supplement with dried seaweed when algae is scarce, and offer some meaty foods (mysis, pellets) as LiveAquaria recommends. A well-fed crab is less likely to hunt tankmates.

Breeding

Females carry eggs under the abdomen; in West Africa egg-bearing females are found from February to April and in August. The larvae are planktonic and long-lived, which may explain how quickly it spreads. It is not bred in home aquaria.

Compatibility and tank mates

Semi-aggressive: small ones are good reef grazers, but large individuals can catch small fish, shrimp and other invertebrates, especially sleeping fish. Reef safe with caution: it does not usually eat corals but may pick at them or steal coral food. Keep one per tank. Eaten by triggers, puffers and large wrasses.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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