A hardy, beginner-friendly Atlantic urchin with short, dense, even spines — the 'pincushion' look — usually in green, but also white, pink or red. A peaceful, fully reef-safe grazer that mows film and hair algae and famously decorates itself with shells, rubble and bits of seagrass for shade.
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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 up to about 11 cm (4.3 in); usually 5-8 cm in the trade, with short even spines.
Lifespan
2–4 years
Social needs
solo
Native region
Western Atlantic and Caribbean (Carolinas to Brazil, Gulf of Mexico)
Origin
New World
Climate
⛅ Subtropical
Water type
🌊 Marine
Family
Toxopneustidae
Genus
Lytechinus
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
Green
The most common form, with green spines over a green-tinged test — the typical 'green pincushion' of the trade.
White / Pale
Whitish to cream form, a natural color variant common in shallow sunlit populations.
Pink / Red
Naturally occurring pink-to-red variant; coloration varies by locality and individual.
Habitat & enclosure
Keep one in an established reef or FOWLR tank of at least 20-30 gallons (75-115 L) with plenty of live rock and an algae film to graze. Maintain reef-stable conditions: temperature 72-80F (22-27C), pH 8.1-8.4, salinity SG 1.024-1.026, alkalinity 8-11 dKH and low nitrate with no ammonia or nitrite.
It comes from shallow seagrass meadows and reef flats of the western Atlantic and Caribbean, from the Carolinas through the Gulf of Mexico to Brazil, so it favors warm, stable, fully marine water. Moderate flow and any reef lighting are fine.
Substrate
A live-rock aquascape provides the grazing surface it depends on; any fine sand or bare-bottom base works underneath. Established algae and coralline growth keep it fed.
Equipment & setup
Standard reef equipment is enough: protein skimmer, live-rock biofiltration, heater and a powerhead for moderate flow. Hold calcium and alkalinity stable to support the test and spines.
Diet
A herbivore that grazes film algae, hair algae, diatoms and coralline off rock and glass. In algae-poor tanks supplement with nori on a clip, algae wafers or blanched greens a few times a week so it does not lose spines or starve.
Behavior & temperament
Peaceful and reliably reef-safe, it ignores corals and inverts and simply grazes. Like other short-spined urchins it can nudge or topple unattached frags and loose rock as it roams, so secure the aquascape. It is an enthusiastic 'decorator,' holding shells, rubble, algae and seagrass over its body with its tube feet for camouflage and sun protection. House one per tank.
Health
Watch for spine loss and a balding test, the classic signs of starvation, copper exposure, poor water quality or low alkalinity/calcium. It is extremely sensitive to copper, rapid salinity or temperature swings and fast acclimation; never use copper meds and never lift it into the air. Inspect new arrivals for bare patches or a soft test. (Educational only, not veterinary advice.)
Tips, DIY & hacks
Drip-acclimate over 1-2 hours and never expose it to air. One of the best beginner urchins for hair- and film-algae control; clip nori in lean tanks. Glue down frags so its grazing can't dislodge them.
Reviewed and signed off by: KinStation Editorial — pre-launch draft (pending DVM review) on 2026-06-09