Red slate pencil urchin

Care at a glance

Overview

The red slate pencil urchin is a hardy, heavy-spined grazer for a saltwater tank without corals. It is an easy urchin to keep alive.

Caring for the red slate pencil urchin

The red slate pencil urchin is not reef safe, so keep it in a fish-only or rubble tank of at least 50 gal (190 L). It is heavy and bulldozes rock and frags. Give it heavy, well-locked rock with holes it can back into, and strong flow. It moves around far more than most urchins, so it needs plenty of floor to cover.

Hold the water at 72 to 81°F (22 to 27°C) and a pH of 8.1 to 8.4. Drip acclimate it, keep nitrate low and keep copper out of the tank.

It grazes coralline algae off the rock. When that runs out, it turns to coral tissue, bivalves and snails. Feed dried seaweed once the rock is grazed clean.

It is peaceful toward fish, but triggers and large wrasses will eat it. There is no record of it breeding in home aquariums.

Good to know

Heterocentrotus mamillatus is a regular urchin in the family Echinometridae. It carries a few dozen thick, blunt, solid spines up to 10 cm long, with a fringe of short flattened spines below them. The spines are usually brick red but sometimes brown or purple, and they fade to chalky pink in the dark. Field studies clock it moving about a meter a night. It is a different animal from the Caribbean slate pencil urchin, Eucidaris tribuloides.

In the wild

The red slate pencil urchin lives on shallow reef crests and surge zones across the tropical Indo-Pacific. Its range runs from East Africa and the Red Sea to the Pacific islands. It is especially common in Hawaii, where it wedges into holes in basalt and coral rock at 8 to 25 m. It hides by day and grazes at night, mostly on encrusting coralline algae with some turf and Ulva.

Common questions

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