Collector Urchin

Care at a glance

Overview

A peaceful, constant grazer that feeds day and night working over algae, making it one of the more effective algae-control animals a reef tank can hold. It is reef safe, leaving coral tissue alone, but true to its collector name it picks up loose shells, rubble, and bits of algae to pile onto its spines as camouflage, and a big specimen can bulldoze small frags or shift light rockwork while foraging, so give it secured aquascaping and keep an eye on anything not glued down. If tank algae runs low, clip on dried seaweed so it does not start looking for other food sources. Like other urchins it needs a slow drip acclimation, since sudden swings in salinity or pH can kill it outright.

In the wild

Collector urchins range across the Indo-Pacific, from East Africa and the Red Sea to Hawaii and French Polynesia, living on open reef flats, seagrass beds, and rubble from just below the surface down to about 30 metres. Juveniles favor rocky cover while larger adults move out onto more open ground to graze. In the aquarium it wants a mature tank with a steady supply of algae to work through, live rock to forage over, and enough open floor space for an animal that can reach 15 cm across.

Good to know

Tripneustes gratilla is a regular urchin in the family Toxopneustidae, with a dark purplish to black test covered in short white spines, sometimes tipped in orange. It is one of the larger reef urchins in the trade, reaching 10 to 15 cm across the test. In the wild it is a voracious grazer of algae and seagrass, capable of stripping up to half of a seagrass bed's growth during peak feeding season, which is why fisheries programs in places like Hawaii have raised and released it specifically to knock back invasive algae on damaged reefs.

Did you know

It is a genuine tool for reef restoration: hatcheries in Hawaii have bred collector urchins by the thousands specifically to release onto reefs overrun with invasive algae, using the same appetite that makes it a good aquarium algae eater to help damaged wild reefs recover.

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