Pencil Urchin (Eucidaris tribuloides)

Max Size: 5 inches
Diet: Omnivore
Temperament: Peaceful
Reef Compatible: No
Minimum Tank Size: 30 gallons

The Pencil Urchin, also known as the Mine or Club Urchin from the Eucidaris genera, boasts a brown body with stubby, thick spines radiating in all directions, surrounded by basal plates. When handling this urchin, it is essential to avoid trying to pry it out of a hole, as doing so may break its spines before it releases its grip. As it matures, its spines may become adorned with coralline and various types of algae.

During the day, the Pencil Urchin seeks shelter among the rocks, while at night, it actively forages for food. It has a particular preference for grazing on algae lawns and preying on smaller invertebrates like sea squirts or sponges. It's worth noting that this urchin can be destructive to corals. To meet its habitat needs, the aquarium should have multiple hiding places and live rock where it can graze. The rock formations must be sturdy as the urchin may dislodge rocks while moving around the tank. Additionally, it is highly sensitive to high levels of copper-based medications and nitrates, which should be carefully monitored to maintain its health. Poor water conditions may result in the shedding of its spines.

Breeding the Pencil Urchin in an aquarium setting is extremely challenging, and there are no distinguishing characteristics to help differentiate its mate.

To ensure proper nutrition, the Pencil Urchin should be offered dried seaweed along with some supplemental animal-based foods.