Pincushion urchin (Tripneustes gratilla) care guide

Group
Other invertebrates
Other names
Collector urchin, Halloween urchin, Echinus gratilla, Sea egg
Family
Toxopneustidae
Origin
Indo-Pacific and Red Sea, from Mozambique to the Tuamotus and Hawaii, with records in the Bahamas, at 2–30 m
Water
saltwater
Maximum size
15 cm
Temperature
23–27°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.026
Minimum tank
300 litres
Care level
intermediate
Temperament
peaceful
Reef safe
with_caution
Lifespan
3–5 years

Care

The collector or pincushion urchin is a short-spined sea urchin of 10–15 cm across. It is usually dark bluish purple with white spines; some have orange-tipped or orange spines. It is called the collector urchin because it covers itself with shells, rubble and bits of algae. It lives on open bottoms and seagrass beds at 2–30 m, while juveniles hide among rocks. Set-up: a large, mature tank of 300 litres or more with plenty of algae and rockwork. It grazes day and night, so it needs a lot of food. Water figures here are general reef guidance rather than from a source. Aim for 23–27 °C, pH 8.1–8.4, dKH 8–12 and stable SG; urchins do not cope with low salinity or fluctuations. Clean-up crew: a strong algae grazer that eats hair algae, macroalgae and seagrass. In Hawaii, hatchery-reared collector urchins have been released to control invasive seaweed. In aquariums it also grazes coralline algae, can pull loose frags and rock over, and may pick up and carry corals as cover. Glue frags down. Handling: its small pincer organs (pedicellariae) can sting; handle with gloves. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never treat a tank holding them with copper, check the label of any fertiliser or medicine, and keep nets and buckets used for copper-treated tanks separate. Sources: Wikipedia (en.wikipedia.org/wiki/Tripneustesgratilla). Checked October 2026.

Diet

A grazer that eats algae, periphyton and seagrass, mainly seagrass fronds in the wild. Feed dried nori or other seaweed, algae wafers and blanched vegetables if natural algae runs low; it will starve in a clean tank.

Breeding

Sexes are separate and it spawns into the water. Larvae stay in the plankton for weeks, which makes rearing a hatchery job. It is farmed in Hawaii, where about a million larvae were used to start one programme.

Compatibility and tank mates

Peaceful towards fish and most invertebrates, but it may bulldoze corals, eat coralline algae and carry off frags. Puffers, triggers and octopus eat urchins. Fine with most reef fish.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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