Gorilla crab (hitchhiker) (Actaea spp.) care guide

Group
Other invertebrates
Other names
Hairy crab, Hitchhiker crab, Xanthid crab, Pilumnus spp. (also called gorilla crabs)
Family
Xanthidae
Origin
Tropical reefs worldwide; arrives on live rock and coral frags
Water
saltwater
Maximum size
5 cm
Temperament
aggressive
Reef safe
no

Care

Gorilla crab is a hobby name for several small, hairy, often brownish crabs that arrive as hitchhikers on live rock and coral frags. Many belong to the genus Actaea (family Xanthidae, about 31 living species), and similar hairy crabs in the genus Pilumnus are given the same name. They are stocky, with thick, short legs, a rounded, often lumpy or granular carapace covered in fine hairs, and strong, dark-tipped claws. How it arrives: hidden inside holes in live rock or among the base of coral colonies. It is nocturnal and is often only spotted at night with a torch, or noticed when snails, small fish or corals start disappearing. Harm: these are opportunistic predators. They kill and eat snails, small hermits, shrimp, small fish and worms, and nip or tear coral tissue and zoanthids. Numbers rarely grow because they do not breed in tanks, but even one large crab can do a lot of damage. Removal and prevention: dip and inspect new rock and frags, and quarantine live rock if possible. To remove a crab, use a baited crab trap (a jar trap with meaty food) overnight, or remove the rock it lives in and flush it out with a jet of saltwater or a brief freshwater dip of the rock. Not every hairy crab is harmful, but gorilla crabs are best removed. Our sources have little on this group; the details here are general hobby guidance, not from a source. This is a pest and should not be sold as livestock. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most invertebrates. Never dose copper in a tank holding this animal, and check fertiliser and medicine labels before use. Sources: Wikipedia (en.wikipedia.org/wiki/Actaea(crab)). Checked October 2026.

Diet

Opportunistic omnivore and predator: snails, small crustaceans, worms, small fish, coral tissue, algae and leftover food.

Breeding

Sexes are separate and females carry eggs under the abdomen, releasing planktonic larvae. They do not breed in home aquariums, so the problem is limited to the individuals that arrived on rock or frags.

Compatibility and tank mates

Not compatible with a reef tank or clean-up crew. Kills snails, hermits, shrimp and small fish and damages corals. Some wrasses and large predatory fish may eat small ones, but trapping is the reliable answer.

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

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