Pencil Urchin (Eucidaris tribuloides)

The Pencil Urchin, Eucidaris tribuloides, also know as the Slate Pencil Urchin, is a unique marine inhabitant predominantly found in the coastal waters of Florida. Characterized by their distinctive cylindrical shape and short, pencil-like spines, these urchins exhibit a range of colors from green and brown to purple. They typically reside in shallow waters, favoring rocky or sandy bottoms.

In an aquarium setting, the Pencil Urchin displays distinct behavioral patterns. During daylight hours, it tends to seek refuge among rocks, while at night, it emerges to forage. Its diet primarily consists of algae and invertebrates such as sea squirts and sponges. However, it’s important to note that Pencil Urchins can be harmful to corals and are not considered reef-safe. They are known to inadvertently cause destruction to coral structures while moving around in search of food.

To accommodate a Pencil Urchin in captivity, the aquarium should be equipped with multiple hiding spots and an abundance of live rock for grazing. The rock formations need to be stable and secure, as the urchin’s movement could potentially dislodge less sturdy structures. As herbivores, Pencil Urchins play a vital role in their natural ecosystem by helping regulate algae growth, thus maintaining a balance in their habitat.