Slate Pencil Urchin

Species/Animal: (Invertebrates) Slate Pencil Urchin (Heterocentrotus mammillatus)

Description:
The Slate Pencil Urchin is a peaceful species that is generally considered reef-safe with caution. It is admired for its thick, blunt spines that resemble pencils, vibrant reddish to maroon coloration, and sturdy body structure. This species is striking and instantly recognizable among urchins due to its large, smooth, slate-like spines which are often used in crafts and traditional jewelry when collected naturally.

Sexual Dimorphism:

• Males cannot be distinguished externally, as urchins lack obvious sexual dimorphism.

• Females/Juveniles appear similar to males; juveniles are smaller, paler in coloration, and their spines are thinner and more delicate until fully grown.

Size & Tank Requirements:
They reach about 6–8 inches in diameter (spine tip to spine tip) and should be housed in aquariums of at least 100 gallons, since they require space for grazing and can grow quite large compared to other urchins.

Habitat Needs:
Provide ample live rock for grazing and stability, with some open sandbed areas for movement. Because of their size and strength, they can easily dislodge rock structures, so aquascaping should be secure and stable. Stable water parameters are important:

• Salinity: 1.020–1.025

• Temperature: 72–79°F

• pH: 8.1–8.4

A secure lid is advisable, not because they jump, but because their strength and movements can push equipment or rockwork.

Diet:
Slate Pencil Urchins are omnivorous grazers, feeding mainly on algae (including coralline algae), biofilm, and detritus. In captivity, they should be supplemented with dried seaweed (nori), macroalgae, spirulina pellets, and occasionally meaty foods like mysis or brine shrimp to maintain health.

Care Note:
Although hardy, they are powerful movers and may knock over corals or unsecured rockwork. They are best suited for larger reef or fish-only systems where their grazing can be beneficial but managed. With proper care, the Slate Pencil Urchin makes a unique and visually impressive addition to marine aquariums.

algae, etc.], and with proper care this fish makes a standout addition to the aquarium.

International Aquatics Quarantine & Guarantee: All fish are checked by marine vets, given a formalin bath, and held for 14 days in copper-treated systems. We feed Selcon-soaked food with Kanaplex and Metroplex during quarantine. Unless marked, all livestock comes with our 15-Day Guarantee. You will receive a video of your fish eating before shipment. On request, we also send photos/videos after arrival at IA. Some species are import-to-order (3-10 business days). Many common species are already cleared or near the end of QT.

Several species will be import-to-order and may take anywhere from 3-10 business days to secure. Once your fish is secured, you will be notified, and the quarantine process will then begin.