Pencil Urchin

Eucidaris tribuloides, the Pencil Urchin, is distinguished by its thick, blunt, pencil-like primary spines that give it a prehistoric, heavily armored appearance unique among commonly available sea urchins. Found in the Caribbean Sea and Atlantic, it grazes on encrusting organisms including coralline algae, sponges, and occasionally coral tissue, making it better suited to fish-only or FOWLR systems than active reef aquariums. Its slow movement and highly distinctive appearance make it a captivating specimen.

House in a FOWLR aquarium rather than an active reef to prevent coral damage. Provide live rock with encrusting organisms for grazing. Supplement with dried seaweed and algae-based foods. Acclimate slowly. Avoid housing with pufferfish and triggerfish that will attack it.