Sally Lightfoot Crab

Quick facts

Identity

Also known as

Nimble Spray Crab; Urchin Crab; Spray Crab

Synonyms

Percnon gibbesii; Acanthopus gibbesi

Environment

Saltwater

Native to

Western Atlantic (Florida to Brazil), Caribbean Sea, eastern Pacific, West Africa; introduced to the Mediterranean Sea

Habitat

Shallow intertidal and subtidal rocky shores, typically 1-2 m deep, hiding in narrow crevices among wave-swept rocks

Sourcing

Wild-caught

Conservation

Not Evaluated

Care

Care level

Easy

Temperament

Semi-Aggressive

Adult size

1.5 – 4 in (3.8 – 10 cm)

Lifespan

2 – 4 yrs

Min tank

30 gal (114 L)

Growth rate

Moderate

Placement

Rock & glass

Water

Temperature

72 – 78 °F (22 – 26 °C)

pH

8.1 – 8.4

dKH

8 – 12 dKH

Salinity

1.023 – 1.025 SG

Flow

Moderate-High

Behavior & compatibility

Social

Solitary

Aggression to own kind

High

Active

Daytime

Reef safe

With caution

Invert safe

With caution

Shrimp safe

With caution

Clean-up role

Algae, Detritus, Leftover food

Population boom risk

Low

Feeding & breeding

Diet

Omnivore

Foods

Algae, Frozen, Pellets, Freeze-dried

Breeding type

Larval (brackish)

Breeding difficulty

Not bred in captivity

Sexing

Adult males have larger, unequal chelipeds compared to the smaller, more uniform chelipeds of females

Target feeding

Beneficial

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Care guide

Overview

Reef tanks with mature, heavily stacked rockwork suit this crab best, giving it the narrow crevices its flattened body needs to escape into between bursts of activity. Mottled green, brown, orange and yellow coloring accompanies constant, rapid movement across rock and glass rather than hiding. Solitary by nature, it tolerates no rival of its own kind and requires a tight lid to prevent escapes.

Care

This crab is one of the fastest movers commonly kept in marine aquariums, spending most of its time skittering across live rock and glass rather than hiding. It needs a mature tank with plenty of stacked rockwork offering narrow crevices to retreat into, since its flattened body lets it wedge into gaps that would stop a bulkier crab. A tight-fitting lid is worth the trouble, as it climbs pipes and cords with ease and will exploit any opening to escape. Stable calcium, alkalinity, and magnesium levels support clean molts, and copper-based medications must be avoided entirely.

Feeding

Juveniles graze mainly on filamentous algae, biofilm, and detritus on rock and glass, making them useful for controlling nuisance algae early on. As they grow, they become more opportunistic and will readily take meaty foods, so offering algae sheets, pellets, and occasional frozen fare keeps them from turning to hunting tankmates. Feeding should be frequent enough that the crab is not left searching for protein on its own.

Tank mates

Adults are best kept singly or as an established pair, since two same-sex individuals sharing a small tank often results in fighting. Small, slow-moving snails, hermit crabs, feather dusters, and resting fish are at some risk once the crab reaches full size, particularly if it is underfed. Avoid pairing with aggressive nippers such as triggerfish or large wrasses that may target its legs, and keep an eye on interactions in smaller or more delicate reef setups.

Breeding

Breeding in home aquariums is essentially unheard of, as females release planktonic larvae that pass through multiple developmental stages in open water. These larvae are almost always lost to filtration or predation long before settling, so captive populations are not sustained through home breeding. All specimens in the trade originate from wild collection rather than aquaculture.

Health

Molting is the period of greatest vulnerability, and a crab caught mid-molt by aggressive tankmates can lose limbs or fail to complete the shed. Leaving the discarded exoskeleton in the tank lets the crab reabsorb minerals from it rather than removing it right away. Stress, unstable salinity, or iodine deficiency can lead to incomplete or failed molts, so consistent water parameters matter more for this species than for many other cleanup crew inverts.

Sources

1. Sally Lightfoot Crab (Percnon gibbesi) Aquarium Care | Atlarium
2. Sally Lightfoot Crab Invertebrate Care Guide | Top Shelf Aquatics
3. The Sally Lightfoot Crab: A Real Character of a Crustacean | Reef Builders
4. Percnon gibbesi (sally lightfoot crab) | CABI Compendium

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