Red Slate Pencil Urchin

The red slate pencil urchin is recognized by the very thick, blunt-tipped, pencil-like spines radiating from its body. The spines range from deep red to reddish brown and have pale bands near the base. The body grows to about 8 cm; with the spines it covers a diameter of more than 20 cm. Its spines are not venomous and do not pierce the skin. It is much larger than the small Caribbean pencil urchin (Eucidaris tribuloides). Those on the market are wild-collected.

• At least 300 liters; wide crevices to shelter in during the day and solidly built, secured rockwork.
• Salinity specific gravity 1.024–1.026, pH 8.1–8.4, temperature 24–27°C; nitrate should be low.
• Reef safe with caution: it does not eat corals, but as it roams it knocks over unsecured frags, can damage tissue as it crawls over corals, and also scrapes coralline algae. Most sources recommend it for fish-only aquariums or reefs with sturdy corals.
• It can climb the glass; the aquarium should have a closed lid. Copper-based medications are lethal.

Herbivorous; it grazes algae on the rocks. If algae are insufficient, nori clipped to a rock, seaweed sheets and algae-based granules should be offered; it can starve in an aquarium with little algae.

Nocturnal; during the day it wedges itself into crevices. It does not attack fish or other invertebrates. Shedding a few spines is normal; losing many spines indicates deteriorating water quality.

Good companions: tangs, clownfish, damselfish, gobies; cleaner shrimp, hermit crabs.

Avoid: triggerfish and pufferfish, large wrasses; unsecured coral frags and narrow, crowded coral gardens; a second large sea urchin in the same aquarium.