The showpiece urchin of the hobby: stout, blunt, brick-red spines (historically used as writing slate pencils) radiating from a dark test. A peaceful, reef-safe coralline grazer prized for its color and sculptural look, though it needs a mature tank with steady coralline and algae to stay fed.
ℹ️
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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Body to about 8 cm (3 in); thick, blunt, triangular red spines up to ~10 cm (4 in) long.
Lifespan
5–10 years
Social needs
solo
Native region
Indo-Pacific and Red Sea, abundant in Hawaii
Origin
Old World
Climate
🌴 Tropical
Water type
🌊 Marine
Family
Echinometridae
Genus
Heterocentrotus
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
Hawaiian Red
The prized bright brick-red form most common in Hawaiian specimens — the look that drives the trade name.
Brown / Purple (Pacific)
Naturally occurring brown, purplish or yellowish-spined variants from other Pacific populations.
Habitat & enclosure
Keep one in a mature, established reef of at least 30-55 gallons (115-210 L) with abundant live rock carrying a healthy crop of coralline and film algae, which it depends on to feed. Maintain stable reef parameters: temperature 72-80F (22-27C), pH 8.1-8.4, salinity SG 1.024-1.026, alkalinity 8-11 dKH, calcium 400-450 ppm and low nitrate.
It is an Indo-Pacific and Red Sea reef animal, especially abundant in Hawaii, living on hard reef structure in moderate water movement. Moderate flow and any reef lighting are fine; stable calcium and alkalinity support its heavy spines.
Substrate
Mature live rock with strong coralline and algae growth is the key requirement; any sand or bare-bottom base works underneath. The more established the rock, the better it feeds.
Equipment & setup
Standard reef equipment suffices: skimmer, live-rock biofiltration, heater and a powerhead for moderate flow. Keep calcium and alkalinity stable (dosing or balanced two-part) to sustain coralline growth and the urchin's spines.
Diet
Primarily grazes encrusting coralline algae plus film and turf algae off rock. Because coralline regrows slowly, supplement with dried seaweed (nori) on a clip and algae wafers a few times a week, and avoid keeping it in a young tank without an established algae base, where it will slowly starve.
Behavior & temperament
Peaceful, slow and reef-safe toward fish, corals and other inverts. Its only real downsides are mechanical: the heavy spines and body can knock loose frags or unstable rock as it moves, so secure the aquascape, and it may graze coralline off display rock and powerhead/glass surfaces. House one per tank.
Health
Hardy once established but a poor shipper if mishandled — like all echinoderms it is extremely sensitive to copper, salinity and temperature swings, low oxygen and air exposure, so drip-acclimate slowly and never lift it out of the water. Faded color, spine loss or a soft test point to starvation or water-quality problems; maintain coralline growth and stable calcium/alkalinity. (Educational only, not veterinary advice.)
Tips, DIY & hacks
Buy only for an established tank with visible coralline, and feed nori to keep it from slowly wasting. Drip-acclimate over 1-2 hours and never expose it to air. Secure frags and rockwork, since its weight can topple loose pieces.
Reviewed and signed off by: KinStation Editorial — pre-launch draft (pending DVM review) on 2026-06-09