Care guide, husbandry, breeding, disease, sourcing, and tankmate intelligence on Slate Pencil Urchin - written by the Fast Aquatics editorial team and cross-verified against vendor records on the live marketplace.
Slate Pencil Urchin (Heterocentrotus mamillatus) is a marine invertebrate kept by aquarists for reef-tank cleanup, biological control of pests, or aesthetic display. Suitable for keepers with 6-12 months of experience and stable water chemistry.
Where Slate Pencil Urchin comes from
Slate Pencil Urchin (Heterocentrotus mamillatus) is native to Indo-Pacific reef ecosystems, with wild populations distributed across coral reefs, sandy lagoons, and rocky tide pools. Captive specimens are typically wild-collected; some species are starting to be aquacultured but most Slate Pencil Urchin sold today still comes from wild reef collection. Sustainable sourcing matters - look for vendors who can verify their collection practices, and consider aquacultured alternatives when available.
Slate Pencil Urchin tank size and setup
Slate Pencil Urchin requires a minimum of 55 gallons for healthy adults. The minimum is based on the species' adult size (8 inches (spines)), territorial range, and behavior pattern. Most Slate Pencil Urchin sold at small juvenile size will reach full adult size within 12-24 months and the system must be sized to the adult, not the juvenile.
For a Slate Pencil Urchin setup: mature reef tank with stable parameters, live rock for cover, sandbed substrate (1-2"), reef-grade lighting if photosynthetic, and a fully-cycled biological filter at least 6 weeks old. Newly-cycled tanks under 6 weeks crash the parameters that Slate Pencil Urchin depends on.
Slate Pencil Urchin requires standard reef parameters held tightly stable: Temperature: 76-80°F (24-27°C) Specific gravity: 1.025 (refractometer-measured) pH: 8.1-8.4 Alkalinity: 8-9 dKH Calcium: 420-450 ppm Magnesium: 1300-1400 ppm Ammonia + nitrite: Both 0 ppm Nitrate: Under 10 ppm Copper: 0 (lethal to invertebrates)
Slate Pencil Urchin is sensitive to copper - never medicate the display tank with copper if Slate Pencil Urchin is present. Stable parameters beat perfect parameters.
What Slate Pencil Urchin eats
Slate Pencil Urchin is a algae grazer. Provides natural algae control by grazing on filamentous, hair, and turf algae throughout the tank. Supplemental nori sheets and algae wafers ensure adequate nutrition when tank algae is depleted. Avoid copper-based algaecides - they kill Slate Pencil Urchin. Feed Slate Pencil Urchin appropriately for its size + activity level. Overfeeding is the #1 cause of water-quality crashes in tanks of all sizes.
Slate Pencil Urchin tankmates and compatibility
Slate Pencil Urchin is generally peaceful and compatible with most reef community species. Avoid keeping with predatory fish that view inverts as food: large wrasses (especially halichoeres + thalassoma), triggerfish, pufferfish, and certain large angelfish. Multiple Slate Pencil Urchin can share a tank but compete for food.
Browse care guides for tankmate-compatibility tables for Slate Pencil Urchin and similar species.
Slate Pencil Urchin adult size and lifespan
Slate Pencil Urchin reaches 8 inches (spines) at adulthood with a captive lifespan of 5-10 years with proper care. Many marine inverts molt periodically; provide adequate calcium and a stable parameter regime to support healthy molts.
Can you breed Slate Pencil Urchin?
Slate Pencil Urchin breeding in captivity ranges from straightforward (some shrimp, snails) to nearly impossible (most starfish, urchins) due to pelagic larval requirements. Captive-bred specimens are increasingly available from sustainable aquaculture facilities; check with vendors before assuming wild-caught origin.
Common Slate Pencil Urchin diseases and problems
Slate Pencil Urchin is sensitive to copper, ammonia spikes, low oxygen, and rapid parameter swings. NEVER use copper medications in a tank with Slate Pencil Urchin. Symptoms of stress: reclusive behavior, color loss, refusal to feed, abnormal molting (incomplete or stuck molts). Most Slate Pencil Urchin deaths trace back to acclimation shock or parameter mismatch - drip-acclimate over 45-60 minutes when adding to a new tank.
Where to buy Slate Pencil Urchin online
Slate Pencil Urchin is sold at LFS (local fish stores), online retailers, and direct from breeders/wholesalers. Pricing varies widely by source, size, and quality:
Browse live Slate Pencil Urchin from vetted Fast Aquatics vendors with carrier-tracked overnight shipping (FedEx Priority + UPS Next Day), climate-aware hold logic, and a 4-hour DOA window with photo-evidence claims. Captive-bred or aquacultured specimens cost more upfront but arrive healthier and integrate faster.
Slate Pencil Urchin FAQ
How big does Slate Pencil Urchin get?
8 inches (spines) at adulthood within 12-24 months.
How long does Slate Pencil Urchin live?
5-10 years with proper care.
What is the minimum tank/pond size?
55 gallons, with larger systems strongly recommended.
Is Slate Pencil Urchin hard to keep?
Slate Pencil Urchin is rated intermediate difficulty.
What does Slate Pencil Urchin eat?
Slate Pencil Urchin is a algae grazer; appropriate diet matches its natural feeding pattern.
Slate Pencil Urchin taxonomy and care recommendations cross-checked against the following authoritative references and our internal vendor + breeder database.