Green Rock Urchin

Geographical Origin and Habitat: Common in the tropical waters of the Caribbean, Gulf of Mexico, and Florida, where it colonizes shallow rocky reefs and seagrass beds.

Taxonomy: Belongs to the class Echinoidea. Features a rounded calcareous test covered with sharp, mobile spines that are circular in cross-section.

Social Behavior: Solitary and nocturnal. Stays wedged in rocky crevices during daylight hours to avoid predators and emerges at night to forage. Predominantly nocturnal and solitary creature. It wedges itself into rocky crevices during the day and emerges at night to graze on benthic algae.

Coloration and Sexual Dimorphism: Spines are green or reddish-green, often with lighter rings near the base. No visible external dimorphism between males and females. The spines exhibit a signature bright green coloration, often with red or purple tips. No external sexual dimorphism is visible.

Tank Setup: Safe with most fish and large invertebrates. Use caution with small corals or frags, as the urchin may knock them over or graze on them. Requires a mature marine aquarium with plenty of stable rockwork, as this urchin can knock over loose corals and unsecured rocks during its movement.

Diet and Feeding: Herbivore. Primarily grazes on film algae, hair algae, and macroalgae. Supplement with dried seaweed (nori) if natural algae levels are low. Herbivorous. Feeds mainly on nuisance algae and detritus. If natural algae levels are low, supplement their diet with dried nori seaweed sheets.

Water Quality: Requires clean, stable marine parameters: temperature 24-27°C, pH 8.1-8.4, SG 1.023-1.026. Keep nitrates below 10 ppm. Keep water parameters stable: temperature 22-27°C, pH 8.1-8.4, specific gravity 1.022-1.025. Calcium and magnesium levels must be kept high for spine health.

Compatibility and Tankmates: Herbivore. Primarily grazes on film algae, hair algae, and macroalgae. Supplement with dried seaweed (nori) if natural algae levels are low. Safe with most reef fish and invertebrates. Do not house with dedicated urchin predators such as triggerfish, large wrasses, or puffers.

Aquarium Breeding: Safe with most fish and large invertebrates. Use caution with small corals or frags, as the urchin may knock them over or graze on them. Spawning in home aquariums is highly unlikely. In nature, gametes are released into the water column, followed by a delicate planktonic larval stage.

Risks and Diseases: Highly sensitive to copper treatments and sudden salinity drops. Dropping spines is a major warning sign of stress or poor water parameters. Extremely sensitive to copper treatments (which are lethal) and sudden drops in salinity. Always use a drip method for proper acclimation.