Green sea urchin

Care at a glance

Overview

Peaceful and simple at the right temperature. It is not a reef tank animal at all: it needs 2 to 15 C, and in a chilled tank it will clear every macroalga and kelp frond within reach. Keep it with other cold North Atlantic or North Pacific animals, feed kelp, dried seaweed, and algae wafers, hold the water cold with high oxygen, drip acclimate it, and never use copper. Sea stars, crabs, lobsters, and wolffish eat it in the wild, so choose tank mates with that in mind. Note that the trade sometimes calls the tropical Lytechinus variegatus a green sea urchin; that is a different animal that takes warm water.

In the wild

The green sea urchin lives on rocky bottom in cold northern water right around the globe, from the Arctic at 81 degrees north down to Maine and Cape Cod, the British Isles, Norway, Puget Sound, Sakhalin, and the Kuril Islands, from the tide line to over 1,000 m. It grazes kelp beds and in places has eaten them down to bare rock. It is the coldest-water urchin in this catalog and needs 2 to 15 C, so a chiller is not optional; a summer spike above about 20 C will kill it. Give it 150 liters or more with rock, strong oxygenated flow, dim light, and water at pH 8.1 to 8.4.

Good to know

Strongylocentrotus droebachiensis is a regular urchin in the family Strongylocentrotidae, named for the town of Drobak on the Oslo Fjord, where Muller described it in 1776. The test averages about 5 cm and reaches 8.7 cm, pale green with short green spines, and it grows roughly 10 mm a year, so its age can be read from its size. It eats kelp and other seaweed and will take small animals, and it tolerates lower salinity than most urchins. It supports a roe fishery in Maine, Canada, Norway, and Russia and is farmed experimentally.

Common questions

Related species

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• 

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• 

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• 

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