Rock boring urchin (Echinometra mathaei) care guide

Group
Other invertebrates
Other names
Burrowing urchin, Rock-boring urchin, Echinus mathaei, Burrowing sea urchin
Family
Echinometridae
Origin
Shallow tropical Indo-Pacific from the Red Sea, Madagascar and East Africa to Hawaii; reefs, down to 139 m
Water
saltwater
Maximum size
5 cm
Temperature
22–27°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.025
Minimum tank
150 litres
Care level
intermediate
Temperament
peaceful
Reef safe
with_caution

Care

The rock boring urchin is a small, short-spined Indo-Pacific urchin with a test (body) about 5 cm across. Colour varies: the body is usually dark, and the spines may be green and purple or green with purple tips. A pale ring at the base of each spine helps identify it. It uses its spines and teeth to grind hollows into coral rock, where it shelters by day. Tank set-up: a mature reef or fish tank of 150 litres or more with plenty of live rock and algae to graze. Be aware that it bores into rock: over time it can deepen holes in live rock and dislodge loose frags and small rocks. It is used as an algae grazer but is less bulldozing than larger urchins. Water: about 22–27 °C, pH 8.1–8.4, dKH 8–12 and specific gravity 1.023–1.025. Like all urchins it is sensitive to salinity swings and poor water quality; acclimatise slowly. Clean-up crew: it grazes algae, coming out at night to feed, including film algae and some coralline algae. It can starve in tanks with little algae, so supplement with dried seaweed. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most invertebrates. This urchin is especially sensitive: studies show copper harms its larvae at 0.02 mg/L and kills adults at around 0.3–0.5 mg/L, levels well below normal treatment doses. Sources: Wikipedia (en.wikipedia.org/wiki/Echinometramathaei). Checked October 2026.

Diet

Herbivore. Grazes film algae, turf algae and some coralline algae from rock. Supplement with dried seaweed (nori) on a clip and algae wafers, especially in tanks with little algae.

Breeding

Sexes are separate and fertilisation is external; adults release eggs and sperm into the water and the planktonic larvae settle after some weeks. In warm waters it breeds all year. It is not bred in home aquariums.

Compatibility and tank mates

Generally peaceful and does not eat corals, but it may knock over or carry off small frags, graze coralline algae and slowly erode rock, so it is reef safe with caution. Eaten by triggers, puffers and some wrasses. A small commensal shrimp sometimes lives among its spines in the wild.

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

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