Decorator Crab

Decorator Crabs (Camposcia retusa and related species) do exactly what the name promises: they actively attach living sponges, algae, colonial tunicates, and other small organisms to hooked Velcro-like bristles covering their carapace and legs, building a genuine, growing camouflage suit out of whatever material is available in their environment. It's not passive debris accumulation — the crab selects and places material deliberately, and a decorator moved to a new tank will often re-decorate itself using locally available organisms within 24–48 hours.

The biology behind this is fascinating: the hooked cuticular projections (setae) on their exoskeleton function like biological Velcro, holding attached organisms in place. The attached organisms typically remain alive and continue growing, which means a well-established decorator crab is carrying a miniature reef of living organisms on its back — including organisms that weren't there when it arrived.

Peaceful, slow-moving, and one of the more genuinely fascinating behavioral quirks you can observe in a reef cleanup crew. They're not aggressive toward corals, fish, or other invertebrates, and their deliberate, unhurried pace means they rarely disturb settled specimens even when climbing across the rockwork.

Scientific name: Camposcia retusa (and related decorator crab species)
Origin: Indo-Pacific — rubble zones, reef slopes, and sponge-rich habitats across tropical reefs
Water parameters: Temp 72–80°F · Salinity 1.023–1.026 · pH 8.1–8.4
Tank requirements: 30 gal minimum; a reef with diverse living organisms gives the crab material to decorate with
Diet: Omnivore scavenger — detritus, algae, and small particulate organic matter; often eats what it collects
Compatibility: Reef safe; peaceful with all species; won't harm corals or fish
Husbandry note: The decoration behavior is directly tied to camouflage — a decorator crab in a bare or sparsely decorated tank will appear underdressed and stressed. A tank with diverse macroalgae, sponge fragments, and varied rubble gives it the palette it needs to fully express this behavior.