Shingle urchin

Care at a glance

Overview

Peaceful and harmless to fish, and it does not eat coral tissue, but it is a reef caution because it strips coralline algae bare and because a reef tank cannot give it the surf it is built for. Most shingle urchins fade over months in still, warm water, though a few keepers report years with one on the glass under very high flow. Keep one, drip acclimate it, feed dried seaweed pressed onto the rock when the coralline is gone, hold nitrate low, and never use copper. It has no venom and can be handled, but its grip is so strong that pulling it off the glass tears its tube feet.

In the wild

The shingle urchin lives on the most wave-beaten intertidal rock in the Indo-West Pacific, from Sri Lanka and the Bay of Bengal through Indonesia to Hawaii, where it is known as ha'uke'uke and is common on black lava shores pounded by surf. It sits in the open in clusters at and just below the tide line, in the top 5 m. No home tank reproduces that. If you try, it needs 200 liters or more with very strong, surging, well-oxygenated flow, bare rock thick with coralline algae, and tropical water at 23 to 28 C with pH 8.1 to 8.4.

Good to know

Colobocentrotus atratus is a regular urchin in the family Echinometridae, the same family as the rock-boring urchin. The dome-shaped test reaches about 10 cm but is usually smaller, and its upper spines are flattened and fused into a smooth mosaic of dark maroon plates like roof shingles, with a skirt of paddle-shaped spines around the rim, giving it a limpet shape that sheds waves. Underneath it has an unusually large number of tube feet, and lab tests found it holds on in water speeds above 17 m per second, roughly three times what a rock-boring urchin survives. It scrapes coralline algae and algal film from rock with its lantern. In Hawaii, where it is most abundant, it is gathered as food, and almost none reach the aquarium trade.

Common questions

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