Purple Pincushion Urchin - Echinometra sp.

Purple Pincushion Urchin (Echinometra sp.)

The Purple Pincushion Urchin (Echinometra sp.) is an attractive marine grazer recognised by its rounded body and dense covering of purple to reddish-purple spines. Also sold as a Purple-Spined Urchin or Rock-Boring Urchin, it spends much of its time moving across live rock and aquarium surfaces in search of algae, biofilm and organic material. This useful clean-up crew animal can assist with controlling nuisance algae in a mature marine aquarium, although it may also consume coralline algae and move unsecured coral fragments or decorations while grazing.

Common Name:
Purple Pincushion Urchin, Purple-Spined Urchin, Purple Rock-Boring Urchin, Rock-Boring Urchin

Scientific Name (Latin):
Echinometra sp.

Maximum Size:
Approximately 8–12 cm across including the spines, depending on the exact species. The hard central test is considerably smaller than the animal’s total visible diameter.

Water Type:
Marine

Origin / Natural Habitat:
Species within the genus Echinometra occur across tropical and subtropical reef regions, including the Indo-Pacific, eastern Pacific, Caribbean and Atlantic, depending on the species.

They are commonly associated with shallow rocky shores, coral reefs, reef flats and rubble zones. Many species shelter within holes, crevices or depressions in rock during daylight hours and emerge more actively after dark to graze.

Water Parameters:
Temperature: 23–27°C
pH Range: 8.1–8.4
Salinity: 1.023–1.026 SG

Temperament:
Peaceful towards fish and other aquarium animals, but physically disruptive. The Purple Pincushion Urchin does not actively attack tank mates, although its strong tube feet and spines can dislodge loose coral pieces, small rocks and decorations.

It should not be kept with triggerfish, large puffers, certain wrasses or other predators known to feed on echinoderms.

Diet:
Primarily an algal grazer and scavenger that feeds on microalgae, short turf algae, biofilm, diatoms, detritus and organic material growing across rock and aquarium surfaces.

In established aquariums, much of its diet may come from natural grazing. Supplementary foods can include dried marine algae, nori, sinking herbivore foods and small pieces of algae-based gel food placed close to its normal grazing area.

Supplementary feeding is especially important in very clean aquariums or where several grazing animals compete for limited algae. Urchins may also consume coralline algae, which is normal feeding behaviour.

Minimum Tank Size:
A minimum aquarium volume of approximately 100 litres is recommended for a single specimen, provided the aquarium is mature and contains sufficient established rockwork and natural algae.

Larger aquariums are preferable because they offer a greater and more reliable grazing area.

Behaviour & Activity:
Usually most active during the evening and at night, although established specimens may also graze openly during the day.

The urchin moves using numerous tube feet located between its spines. It may carry small shells, rubble, algae or other loose material on its body as camouflage and protection.

Many Echinometra species shelter within rock crevices or excavated depressions. They may gradually scrape soft limestone and calcareous rock while creating or enlarging a preferred refuge.

Reef Safe:
Reef Safe with Caution

The Purple Pincushion Urchin does not normally consume healthy coral tissue and is generally suitable for established reef aquariums. However, it may scrape coralline algae from rockwork and can dislodge unsecured coral frags, small colonies, shells and decorative items.

Very hungry animals may graze close to encrusting corals or other sessile organisms. Corals and rockwork should be firmly secured before introduction.

Special Requirements or Care Notes:
Introduce only to a mature, fully cycled marine aquarium with stable salinity and sufficient algae or biofilm to support continuous grazing.

Sea urchins are sensitive to rapid changes in temperature, pH and salinity. Slow acclimatisation is strongly recommended, and the animal should remain submerged whenever practical during transfer.

Like other echinoderms, urchins are highly sensitive to copper-based medications and poor water quality. Never expose the animal to copper treatments, and avoid sudden changes in nitrate, salinity or other water parameters.

Provide stable live rock containing caves, crevices and shaded areas. Secure all corals, small rocks and loose decorations with suitable reef-safe adhesive before adding the urchin.

Do not lift the animal by its spines. Use a submerged container when movement is necessary and allow the tube feet to release naturally rather than pulling it from the rock or glass.

A loss of spines, prolonged inactivity, failure to attach firmly or remaining overturned can indicate starvation, poor water quality or severe stress and should be investigated promptly.

Because animals sold under this trade name may represent different purple-coloured urchin species, final adult size, spine length and grazing intensity can vary.

Suitable for:
Beginner to intermediate fishkeepers

Availability:
Occasional in trade

All images are a visual representation of the animal you will receive, made to be as accurate as possible. Please note that Mother Nature is a wonderful thing, and variation in patterns and colours will occur — that is part of the unique beauty of these animals.