TankBud

Decorator crab

Camposcia retusa

Also known as Spider decorator crab, Decorator spider crab, Camposcia decorator crab, Velcro crab

SaltwaterCrab

Care at a glance

Temperature
72–81°F
22–27°C
pH
8.1–8.4
Adult size
1.2 in
3 cm
Minimum tank
26 gal
100 L
Temperament
Mostly peaceful
Social behavior
Solitary
Tankmates
With caution
Swim level
Bottom
Diet
Carnivore
Difficulty
Medium
Breeding
No record
Rarity
Common
Reef safe
Reef safe with caution
Family
Inachidae
Origin
Indo-West Pacific, from the Red Sea and East Africa to Japan and Australia

Overview

The decorator crab is a slow, nocturnal scavenger that dresses itself in bits of reef for camouflage. It suits a keeper with a little experience.

Did you know

The decorator crab was given craft pompoms to decorate with in a 2017 study by Brooker and colleagues. It dressed much faster when it had nowhere to hide, mostly covering its carapace and back legs, the parts a predator sees first. The camouflage is a substitute for shelter, not a fashion choice.

Caring for the decorator crab

Give a decorator crab a mature tank of at least 26 gal (100 L), with live rock and rubble. Add macroalgae or sponge it can harvest for camouflage. After each molt it has to dress again, and given material it covers itself within a day. Plan dim or moonlit periods when you can watch it feed.

Keep the water at 72 to 81°F (22 to 27°C) and a pH of 8.1 to 8.4. Hold the specific gravity at 1.023 to 1.025. Acclimate it slowly, since some imports fail in the first weeks. Feed it directly after lights out with mysis, chopped clam, fish and krill a few times a week, so it does not go looking.

The decorator crab is mostly peaceful and safe with fish, but hard on the smallest inverts. It clips zoanthids, sponge and soft coral to decorate with, and sometimes eats what it clipped. It may also take a small snail or hermit crab.

These habits make it reef safe only with caution. In a big tank with cheap soft corals it is a curiosity, but in a frag tank it is a menace. Most keepers house one per tank. It has not been bred in aquariums.

Good to know

The decorator crab is the only species in the genus Camposcia, a spider crab in the family Inachidae described by Latreille in 1829. Its long thin legs give a span of up to 10 cm, and retailers quote 4 inches for that reason. Its body and legs are covered in hooked setae that work like velcro, and it is also sold as the velcro crab. It snips off pieces of sponge, algae, hydroid and soft coral and presses them on until it looks like a lump of reef. It lives about three to five years.

In the wild

Camposcia retusa lives on coral reefs and rubble across the Indo-West Pacific, from the Red Sea and East Africa to Japan and Australia. It ranges from the shallows down to more than 200 m. It spends the day motionless against rock and moves at night.

Common questions

What size tank does a decorator crab need?

A decorator crab needs at least 26 gal (100 L). It spends most of its time in the bottom.

What temperature and pH does a decorator crab need?

A decorator crab is comfortable at 72–81°F (22–27°C) with a pH of 8.1–8.4.

What does a decorator crab eat?

A decorator crab takes mysis, chopped clam, fish and krill, fed right after lights out a few times a week. It also sometimes eats the zoanthids, sponge and soft coral it clips.

How big does a decorator crab get?

An adult decorator crab reaches about 1.2 in (3 cm).

Related species