Slate pencil urchin

Care at a glance

Overview

The slate pencil urchin is a hardy, peaceful grazer for the rockwork of a mature saltwater tank. It is easy to keep.

Caring for the slate pencil urchin

Give the slate pencil urchin a mature tank of at least 20 gal (75 L). It needs an established growth of coralline and film algae to browse. Build sturdy, well-secured rockwork with plenty of caves, since a determined urchin can topple loose rock as it moves. Never pull it out of a hole by force, because the primary spines snap off easily and do not grow back quickly.

Keep the water at 75 to 81°F (24 to 27°C) and a pH of 8.1 to 8.4. Urchins are unusually sensitive to sudden shifts in salinity or pH, so drip acclimate it slowly over an hour or more.

Its diet leans on algae, especially coralline algae. It is a genuine omnivore, though, and also picks off sponges, small bivalves and other invertebrates it runs across. Offer dried seaweed and the occasional meaty food, so it has less reason to go looking elsewhere.

The slate pencil urchin is peaceful and rated reef safe with caution. A well-fed one in a large reef mostly leaves things alone. A hungry one will graze down coralline algae, and it has been known to nip at soft corals.

Its spawning in the wild tracks lunar and seasonal cycles. Florida populations reproduce most heavily in late summer and early fall.

Good to know

Eucidaris tribuloides is a cidaroid urchin in the family Cidaridae, one of the oldest urchin lineages alive today. That lineage has barely changed in millions of years. It carries short, blunt, pencil-thick primary spines in place of the thin needle spines most urchins have. Its dark brown to reddish test is usually hidden completely under the spines. Like other echinoids, it grazes with a five-toothed jaw called Aristotle's lantern and moves on rows of tube feet.

In the wild

Slate pencil urchins live throughout the western Atlantic and Caribbean, from North Carolina down to Brazil. A separate population lives across the ocean, around Cape Verde and the Gulf of Guinea. By day they wedge themselves under ledges and into reef crevices, anchored by their primary spines. They come out at night to graze.

Common questions

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