Pencil Urchin
Eucidaris tribuloides
| Identification | Highly distinctive thick, blunt, club-shaped spines resembling pencils or thick thorns. Reddish-brown to tan body. Dramatically different appearance from typical needle-spined sea urchins. |
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| Maximum Length | 3 inches |
| Origin | Caribbean, Atlantic |
| Minimum Tank Size | 30 gallons |
| Reef Compatibility | With caution — may consume soft corals and sponges |
Behavior
Slower-moving than most other aquarium urchins. A classic "living fossil" — pencil urchins have changed little in appearance over hundreds of millions of years. Hardy and long-lived in captivity. More of a curiosity specimen than a dedicated algae cleaner.
Diet & Feeding
Omnivore. Grazes on algae, encrusting sponges, and organic detritus. May consume soft corals and encrusting organisms if algae is scarce. Supplement with nori and meaty foods.
Cautions
May consume sponges, soft corals, and encrusting invertebrates — not safe in all reef setups. Supplement with food regularly to reduce predation on tank inhabitants. Thick spines can damage coral tissue on contact when moving across rockwork.