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Red pencil urchins (also Slate pencil urchin) are striking reef inverts with thick blunt red-orange spines that resemble pencils. Excellent algae eaters and reef cleaners but their substantial body bulk and bulldozer behavior can knock over loose corals and rockwork. Stunning specimens that demand secured aquascaping.
Native range: Indo-Pacific. Most US trade specimens come through marine wholesale suppliers in Indonesia, the Philippines, Hawaii, and the Caribbean. Wild collection remains the primary sourcing method for the majority of marine inverts - few are captive-bred at commercial scale. Quality of acclimation at the wholesale/retail stage is the biggest single predictor of long-term survival in home aquaria.
Tank size: 50 gallons. Parameters: temperature 74-82°F, salinity 1.024-1.026, plus the standard reef tank requirements - stable calcium 420-440 ppm, alkalinity 8-10 dKH, magnesium 1300-1400 ppm, nitrate under 25 ppm, phosphate under 0.05 ppm. The species requires conditions consistent with a healthy reef tank rather than nutrient-stripped sterile water - well-established systems with diverse microfauna and biofilm typically support these inverts better than newly-cycled tanks.
Lighting: depends on species. Photosynthetic inverts (clams, anemone-symbiotic species) require high-PAR reef LED lighting. Filter-feeders (worms, scallops) prefer moderate lighting and benefit from particulate-rich water. Flow: moderate, indirect flow works for most inverts - direct high-velocity flow stresses or damages soft-bodied species.
Acclimation: drip acclimate over 2-4 hours for hardy species, 4-8 hours for sensitive species (Linckia stars, sea hares, demanding nudibranchs). Never expose inverts to air during transfer - capture in a bowl underwater and transfer wet.
Red Pencil Urchin diet: Algae, dead matter, occasional coralline scrape. Feeding strategy depends on dietary type. Algae eaters require established tanks with biofilm and microalgae growth - new tanks lack the algal base they need. Carnivore inverts (starfish, some snails) need targeted meaty feedings 2-3x weekly. Filter feeders (clams, worms, scallops) need phytoplankton in the water column. Photosynthetic species need adequate lighting plus supplemental amino acid or coral food dosing.
Safe: Reef-safe community with secured rockwork.
Avoid: Tanks with loose coral frags or precarious aquascape.
Not captive bred.
Rockwork toppling (most common); coralline depletion; spine loss from rough handling.
Coral-safe but will scrape coralline algae aggressively. Not safe for tank stability if rocks are loose.
No - they eat algae and detritus. They will scrape coralline algae from rock surfaces.
$25-60 each.
No - blunt spines are mechanically harmful only. Less dangerous than long-spine or globe urchins.
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