Pencil Urchin (Eucidaris tribuloides)

Eucidaris tribuloides belongs to a lineage of urchins that's barely changed since the Triassic, and the thick, blunt spines behind its common name are essentially the same design that's been grazing reefs for a couple hundred million years — a stark contrast to the thin, needle-sharp spines on most other urchins in the trade. That blunt profile makes it a much safer urchin to handle, though it'll still graze coralline algae and the occasional coral polyp if algae runs short, so it's not entirely hands-off in a reef. Slow-moving and mostly nocturnal, spending daylight tucked into crevices with just the spine tips showing.

Care level: Easy · Temperament: Peaceful · Max size: ~3" body (spines add reach) · Min tank: 30 gal · Reef safe: With caution (may graze coral/coralline) · Diet: Omnivore, algae + detritus