Pencil Urchin (Eucidaris tribuloides)
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
At a glance
- Scientific name
- Eucidaris tribuloides
- Common name
- Pencil Urchin
- Water type
- Saltwater
- Care level
- Easy
- Temperament
- Peaceful
- Max size
- ~3" body (spines add reach)
- Minimum tank
- 30 gal
- Diet
- Omnivore, algae + detritus
- Reef safe
- With caution (may graze coral/coralline)
When it ships
Most non-quarantined stock goes out the week you order. If we do not already have the animal in-house we source it first — allow up to two weeks for it to reach us. Live animals leave Monday and Tuesday, and Early AM Overnight is the only service that carries a live arrival guarantee.
The live guarantee
Shipped Early AM Overnight: a 1-hour DOA window from confirmed delivery, and nothing beyond it. Next Day Air and 2-Day carry no live arrival guarantee, and neither does USPS Priority. Local pickup or local delivery: 24 hours, if you bring a water sample from your aquarium and we test it before the animal goes home. Maintenance clients: 60 days when we service the aquarium at least twice a month, 28 days on a monthly plan.
Expert guidance
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