Why is my Pincushion Urchin carrying shells and rocks on its back?

This is a natural behaviour known as 'decorating'. They use their tube feet to place small rocks, empty snail shells, and macroalgae on their backs to camouflage themselves from predators and shield themselves from strong light.

Will a Pincushion Urchin eat my corals?

They are generally considered reef safe and will focus entirely on algae. However, as they move across the rockwork, they can accidentally dislodge loose coral frags or, very rarely, nip at soft corals if completely starved of algae.

How can I tell if my urchin is starving?

A starving or highly stressed urchin will become sluggish and start dropping its spines. If you notice bare patches on the urchin's test, you must urgently supplement its diet with dried nori and check your water parameters.

Can I keep a Pincushion Urchin in a newly set up aquarium?

No, they should only be added to mature aquariums (at least 6 months old) that have an established crop of algae on the live rock for them to eat.

Do Pincushion Urchins need calcium supplementation?

Yes, like corals, urchins require stable calcium and alkalinity levels to maintain their protective exoskeleton (test) and regenerate their spines.

MarineMarineBeginner

Pincushion Urchin

Lytechinus variegatus

The Pincushion Urchin is an industrious and peaceful invertebrate, highly prized in the marine hobby for its insatiable appetite for nuisance algae.

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Ideal Conditions

Temperature: 22 – 26 °C
pH range: 8.1 – 8.4
Hardness: 15 – 20 dGH
Salinity: 1.023 – 1.025 SG
Adult size: 8 – 11 cm
100L minimum: 100 litres+
Lifespan: 3 – 5 years
Diet: Herbivore
Water flow: Moderate
Preferred setup: Established live rock with plenty of grazing surfaces

About the Pincushion Urchin

Scientifically known as Lytechinus variegatus, the Pincushion Urchin is a staple member of the marine clean-up crew. Instantly recognisable by its short, dense spines and somewhat flattened spherical test, this urchin spends its days methodically scraping algae from live rock and aquarium glass. They are famous for their endearing, albeit sometimes frustrating, habit of picking up loose objects to use as camouflage and protection from ultraviolet light.

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Is it right for your tank?

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Where Pincushion Urchin comes from

Native range

Caribbean Sea, Gulf of Mexico, Western Atlantic

Countries / regions

United States, Bahamas, Brazil, Mexico

Habitat

Shallow coastal waters, seagrass beds, and tropical coral reefs.

Commonly found in calm, shallow waters with abundant turtle grass.

Similar species

Collector Urchin
Tripneustes gratilla
Tuxedo Urchin
Mespilia globulus
Longspine Urchin
Diadema antillarum

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Ocellaris Clownfish
Amphiprion ocellaris
Peaceful fish that occupy higher levels of the water column and will ignore the urchin entirely.
Great
Yellow Tang
Zebrasoma flavescens
Fellow herbivores that co-exist peacefully, though they may compete for algae in smaller tanks.
Great
Turbo Snail
Turbo fluctuosus
Excellent clean-up crew companions that share peaceful grazing habits without conflict.
Great
Halloween Hermit Crab
Trizopagurus strigatus
Large, opportunistic hermit crabs may occasionally pick at the urchin or attempt to steal the debris it uses for camouflage.
Compatible with caution
Clown Triggerfish
Balistoides conspicillum
Triggerfish are natural predators of sea urchins and possess the jaw strength to easily crush their protective tests.
Not recommended
Dogface Puffer
Arothron nigropunctatus
Pufferfish actively hunt hard-shelled invertebrates and will predate heavily on the urchin.
Not recommended

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