A rugged, slow-moving urchin with thick, blunt, brown 'pencil' spines that wedge it into crevices by day. Charmingly primitive-looking and hardy, but only conditionally reef-safe — it is more scavenger/omnivore than algae specialist and will nibble sessile inverts, sponges and even coral tissue at night.
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Educational only. KinStation content is reviewed by licensed veterinarians but cannot replace an in-person exam. Always consult a licensed veterinarian or board-certified specialist for diagnosis, treatment, or any decision affecting your pet's health.
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Test about 5 cm (2 in); thick, blunt, brown pencil-like primary spines.
Lifespan
5–10 years
Social needs
solo
Native region
Western Atlantic and Caribbean (Cape Hatteras to Brazil, Gulf of Mexico)
Origin
New World
Climate
⛅ Subtropical
Water type
🌊 Marine
Family
Cidaridae
Genus
Eucidaris
Part of the Sea Urchins
Spiny echinoderm grazers prized as reef clean-up crew for mowing down film, hair and nuisance algae. Most are reef-safe but may dislodge loose corals, and all are highly intolerant of copper and sudden salinity changes.
How this animal changes through its life — each stage often has its own care, diet and space needs.
Photo coming soon
Larva
Most marine invertebrates hatch into microscopic planktonic larvae (such as the zoea of crustaceans or the bipinnaria/veliger of echinoderms and mollusks) that drift and feed in the water column. The larva looks nothing like the adult and undergoes major reorganization.
Photo coming soon
Juvenile
After settling out of the plankton, the juvenile takes on a recognizable miniature of the adult body plan — a tiny shell, a small star, or a translucent shrimp. Crustaceans grow by molting, shedding the exoskeleton to enlarge.
Photo coming soon
Adult
Adults reach full size and reproductive maturity with the species' mature shell, shape, or coloration. Many continue to molt or grow throughout life, and some show sex differences in size or claw/appendage shape.
Color & pattern variants
Natural variants occur in the wild; selectively bred (man-made) variants were developed in captivity.
Natural
Brown (typical)
The standard form, with thick brown blunt spines, often algae- or coralline-encrusted, over a small dark test.
Habitat & enclosure
Keep one in an established reef or FOWLR tank of 20-30 gallons (75-115 L) or more with plentiful live rock and crevices it can jam itself into during the day. Maintain stable marine parameters: temperature 72-80F (22-27C), pH 8.1-8.4, salinity SG 1.024-1.026, alkalinity 8-11 dKH and low nitrate.
It is native to the western Atlantic and Caribbean, from Cape Hatteras through the Gulf of Mexico to Brazil, living among rubble and reef rock. Moderate flow and any reef lighting are fine; it is nocturnal and reclusive.
Substrate
Provide live rock with tight crevices and overhangs it can anchor into with its thick spines; rubble and caves suit it. Any sand or bare-bottom base works underneath.
Equipment & setup
Standard reef equipment is enough: skimmer, live-rock biofiltration, heater and moderate flow. No special lighting is needed for this nocturnal grazer.
Diet
An omnivore and opportunistic scavenger rather than a dedicated algae mower: it eats detritus, algae, and biofilm, but in nature also grazes on sponges, small corals and other sessile invertebrates. In the tank offer dried seaweed, algae wafers and the occasional meaty morsel, and don't rely on it alone for algae control.
Behavior & temperament
Slow, shy and nocturnal, spending the day wedged in a crevice and emerging at night to forage. Generally peaceful, but NOT fully reef-safe — it may nip LPS polyps, clam mantles, sponges, tubeworms and tiny sessile inverts, and its blunt spines can knock loose frags. Keep one per tank in a robust reef or FOWLR rather than a delicate prized reef.
Health
Hardy and long-lived for an urchin, but like all echinoderms it is highly sensitive to copper, salinity swings, low oxygen and air exposure — never use copper meds or lift it from the water. Spine loss and lethargy indicate poor water quality or starvation. (Educational only, not a substitute for advice from an aquatic veterinarian.)
Tips, DIY & hacks
Drip-acclimate slowly and never expose it to air. Choose it for personality and reef-rubble cleanup, not as a primary algae control, and watch prized corals and clams for nighttime nibbling. Its sturdy blunt spines make it the safest urchin to handle, but still move it with care.
Reviewed and signed off by: KinStation Editorial — pre-launch draft (pending DVM review) on 2026-06-09