Red Needle Urchin

Red Needle Urchin: The Spiny Reef Defender

The common name Red Needle Urchin most often refers to specimens of the Long-Spined Sea Urchin genus, Diadema, that exhibit a reddish-brown or burgundy coloration, particularly Savigny's Long-spine Urchin (Diadema savignyi) or color variants of the Black Longspine Urchin (Diadema setosum). These tropical urchins are easily identified by their extremely long, thin, and brittle spines, which are their primary defense mechanism.

These urchins are highly effective members of the cleanup crew, acting as voracious nighttime algae grazers that can keep filamentous and undesirable algae in check. While the test (body) size is relatively modest at around 3-4 inches (8-10 cm), their needle-like spines can easily extend for 6 to 10 inches (15-25 cm) in all directions, making them appear significantly larger and requiring a tank size of at least 55 gallons for a single specimen to move freely.

Hobbyists must exercise extreme caution with this species. Its long, sharp spines are mildly venomous, and the spines are designed to break off easily and embed deep into the skin, causing intense pain and a risk of secondary infection. They are a magnificent addition to a mature system but demand respect and stable water quality.

Diet & Compatibility:

• Diet: This urchin is a dedicated Herbivore / Algivore. It actively grazes on filamentous, film, and detrital algae across the rockwork and substrate, making it one of the best controllers of nuisance algae.
• Feeding: If the aquarium is pristine and algae is scarce, supplemental feeding is required to prevent starvation (which results in spine loss). Offer dried seaweed (Nori), vegetable-based flakes, or algae wafers, typically by target-feeding at night.
• Reef Compatibility: Reef Safe With Caution. They are not known to eat coral tissue, but their long spines and movement can easily knock over unsecured coral frags and rockwork. They can also graze desirable coralline algae. They are generally safe with most ornamental invertebrates (snails, shrimp) but will be eaten by natural predators like Pufferfish and Triggerfish.
• Temperament: Peaceful / Nocturnal. They spend much of the day hiding in rock crevices or huddled together. They are not aggressive toward tankmates, but tankmates that bump into the spines can be injured.
• Venomous Spines: The sting is painful and often results in broken spines lodged in the skin, which can cause a serious localized reaction and infection. Though the venom is mild, seek medical attention to safely remove the spines and prevent infection. Never handle this urchin without protection.

Quick Facts

• Scientific Name: Likely Diadema savignyi or Diadema setosum (Red color variant)
• Primary Common Name: Red Needle Urchin, Banded Diadem Urchin, Long-Spined Urchin
• Other Common Names: Longspine Urchin
• Origin: Indo-Pacific (Widespread Tropical)
• Max Size: 3-4 inch test, but 10-12 inch total span (including spines)
• Temperament: Peaceful / Nocturnal (Spines are venomous)
• Diet: Herbivore / Algivore (Requires heavy algae or supplemental feeding)
• Minimum Tank Size: 55+ Gallons
• Reef Compatibility: With Caution (May knock over frags; excellent algae control)