Longspine Urchin

Black Longspine Urchin – Diadema setosum

The Black Longspine Urchin is a striking invertebrate with a predominantly black body, a central red eyespot, and long, thin black spines. Adults can reach up to 10–12 inches in diameter including spines. Though delicate in appearance, this nocturnal urchin is highly capable of self-defense, using its venomous spines to deter predators - or the unwary reef keeper. It is an effective algae grazer, particularly useful in aquariums with aggressive fish that may consume smaller invertebrates.

Provide a well-established tank with ample hiding places and open substrate for grazing and movement. These urchins are nocturnal, hiding during the day and emerging at night to feed. Introduce them only to stable systems with low nitrates and no copper-based medications. Monitor water quality carefully, as shedding of spines indicates stress or poor conditions.

As an herbivorous grazer, supplement the Black Longspine Urchin’s diet with dried seaweed, such as Julian Sprung’s Sea Veggies, or other algae clips to ensure adequate nutrition in aquaria with limited natural algae growth.

This species also acts as a host for juvenile Banggai Cardinalfish (Pterapogon kauderni), as their young will hide between their spines as they mature.

Approximate product size: 1–1.5" body size