Spider Crab (Camposcia retusa) M

Overview

The Spider Crab Camposcia retusa is one of the most distinctive marine invertebrates available for the home aquarium. With its long, delicate legs and clever camouflage behaviour, this species brings real character to a saltwater display. Often called the decorator spider crab, it is known for attaching bits of algae, sponge and debris to its body, helping it blend into its surroundings in the wild.

This medium-sized specimen is best suited to established marine aquariums with stable water conditions, plenty of rockwork and hiding places. It is a fascinating animal to observe, especially during feeding and when exploring the tank at night. While generally peaceful, it is still a crab and should be housed with care, particularly around small ornamental invertebrates and very slow-moving tank mates.

At Tropical Fish Co, we supply healthy marine livestock with a live arrival guarantee and fast UK delivery, so your new spider crab arrives in excellent condition and ready to settle into its new home.

Care at a Glance

Origin & Natural Habitat

Camposcia retusa is found in the Indo-Pacific, where it inhabits shallow coastal reef environments, lagoons and areas rich in coral rubble, algae and sponges. In nature, it relies on camouflage to avoid predators, decorating its body with materials from the surrounding habitat. This behaviour is not only fascinating to watch, but also a reminder that the species thrives best in a complex environment with plenty of natural textures and hiding places.

The spider crab spends much of its time moving slowly across the substrate and rockwork, picking at food and exploring crevices. It is not a strong swimmer and is not suited to open, bare aquariums. A mature marine setup with live rock, stable salinity and low to moderate flow is ideal.

Tank Setup & Water Parameters

A well-established marine aquarium is essential for this species. Aim for a tank of at least 150 litres, though larger systems are always better for long-term stability and to provide enough territory. Use plenty of live rock to create shaded ledges, overhangs and caves. Fine sand or mixed reef substrate is suitable, but the crab will appreciate areas where it can forage naturally.

Because spider crabs are excellent climbers, the tank should have a secure lid or tightly fitted cover to prevent escapes. Gaps around pipework and cable openings should be blocked where possible. Stable water quality is more important than chasing exact numbers, so keep nitrate low and avoid sudden swings in salinity or temperature.

Recommended parameters: temperature 22–26°C, pH 8.1–8.4, marine salinity 1.023–1.025 specific gravity. Moderate filtration and regular maintenance will help maintain excellent water quality. Provide gentle to moderate flow and avoid strong currents that may stress the crab or make feeding difficult.

As with all crustaceans, moulting is a vulnerable period. Ensure there are secure hiding spots and do not disturb the crab if it becomes inactive or hides for extended periods. A calcium-rich marine environment supports healthy shell development and successful moulting.

Feeding Guide

Camposcia retusa is an omnivorous scavenger with a varied diet. In the aquarium it will accept a range of meaty marine foods and prepared sinking foods. Offer a mix of frozen mysis, chopped prawn, krill, marine pellets, algae-based foods and small pieces of seafood. It will also graze on natural biofilm and leftover food in the tank.

Feed small amounts several times per week, adjusting based on tank maturity and how much natural food is available. Avoid overfeeding, as uneaten food can quickly affect water quality. Using feeding tongs can help target food near the crab without disturbing other inhabitants. A varied diet is best for long-term health and colouration.

Tank Mates / Compatibility

This species is generally peaceful, but it is opportunistic and may take very small, weak or sleeping tank mates if given the chance. It is best kept with calm marine fish that are too large to be considered prey and with robust invertebrates that can hold their own. Avoid pairing with tiny ornamental shrimp, very small crabs, or delicate sessile invertebrates that may be disturbed.

Suitable companions include peaceful reef fish such as clownfish, gobies, blennies and some wrasses, provided the aquarium is large enough and the crab has plenty of space. It is usually best to avoid aggressive triggers, large predatory fish, puffers and species known to nip at crustaceans. As always, individual behaviour can vary, so careful observation is important when introducing any new tank mate.

Because this crab is a climber and a scavenger, aquascaping should include secure rockwork and sheltered zones. This helps reduce stress and gives the animal a natural area to explore without constant competition.

Why Buy from Tropical Fish Co

At Tropical Fish Co, we understand that marine invertebrates need careful handling, reliable packing and prompt dispatch. That is why we offer fast UK delivery and a live arrival guarantee on eligible livestock orders, giving you confidence when buying online. Our team focuses on healthy, well-conditioned animals and clear care information so you can provide the best possible home from day one.

When you choose our Spider Crab Camposcia retusa, you are adding a truly eye-catching marine species to your aquarium — one that rewards patient keepers with unique behaviour and a striking natural appearance. If you are looking for an unusual invertebrate with personality, this is an excellent choice for a mature saltwater setup.