Shingle Sea Urchin - Colobocentrotus atratus

Shingle Sea Urchin AKA Helmet Sea Urchin– Colobocentrotus atratus

Unique features

This compact, sturdy sea urchin grazes on algal film and fine growth on hard surfaces.

A natural grazer for rockwork and stone surfaces with a healthy supply of biofilm.

Adds movement and natural grazing behaviour to a stable marine aquarium.

Needs good water quality, ample grazing surfaces, and a well-established aquarium.

Its flattened, helmet-like shape is adapted to exposed coastal areas with strong water movement, while aquarium conditions should remain stable.

Description

Also known as the helmet urchin, Colobocentrotus atratus is a distinctive algae-grazing species suited to established marine aquariums. Its flattened body and short, robust spines help it hold firmly to hard surfaces. As it moves through the aquarium, it feeds on algal film, biofilm, diatoms, and other fine growth.

Provide a well-cycled aquarium with live rock, suitable grazing surfaces, and peaceful marine aquarium fish. Sea urchins can be sensitive to sudden changes in salinity, temperature, and water quality, so maintain stable conditions and acclimate gradually. Reliable marine aquarium equipment can help support consistent aquarium conditions.

Care & Behaviour

This peaceful grazer slowly explores rockwork, glass, and other hard surfaces. Although adapted to wave-swept coastal habitats, it needs stable aquarium conditions and a reliable food supply in captivity. It can help graze on film and early growth, but is not a remedy for severe algae problems. Secure loose shells, coral frags, and decorations, as the urchin may shift objects as it moves.

Diet

Colobocentrotus atratus primarily grazes on naturally occurring algae film, biofilm, diatoms, and fine growth. If the aquarium offers limited natural food, supplement its diet with seaweed or suitable herbivore food. Browse fish and coral foods for options, and monitor its grazing activity and body condition.

Specifications

Scientific name: Colobocentrotus atratus

Category: Invertebrates / sea urchins

Care level: Moderate

Temperament: Quiet and peaceful

Diet: Algal film, biofilm, diatoms, and supplemental seaweed

Maximum size: Approximately 7–9 cm

Reef safe: Generally, but secure loose frags and decorations

Details: A flattened, sturdy algae grazer that needs stable water conditions and ample grazing surfaces.

Compatible tankmates

Suitable companions include peaceful reef fish, snails, and non-aggressive shrimp. Avoid triggerfish, large wrasses, aggressive crabs, and other animals that may injure or overturn the urchin. Secure corals, rockwork, and small decorations to reduce the chance of them being displaced during grazing.