Purple/Blue Tuxedo Urchin

Commonly referred to as the Blue Tuxedo Urchin or Sphere Urchin, the Tuxedo Urchin is one of the most effective, functional, and visually striking members of a marine aquarium cleanup crew. Characterized by five distinct, velvety vertical bands of deep blue or black separated by rows of short, colorful spines (ranging from red and orange to brown), this invertebrate looks as sharp as its name implies.

​Beyond its dapper appearance, the Tuxedo Urchin is a relentless scavenger. It spends its days and nights vacuuming rockwork and glass, making it an invaluable asset for controlling nuisance algae in reef and marine setups.

​Quick Care Parameters

Care Level Easy to Moderate

Minimum Tank Size 20 Gallons (Requires established rockwork)
Temperature 72°F – 78°F
Salinity / Specific Gravity 1.023 – 1.026 (Crucial for osmotic health)
pH 8.1 – 8.4
Alkalinity (dKH) 8 – 12
Nitrate / Phosphate Low (Sensitive to poor water quality)
Temperament Peaceful
Reef Safe Yes

Key Features & Behaviors

​The Ultimate Algae Eater: Tuxedo Urchins have a specialized mouth structure known as Aristotle's lantern, which they use to scrape rocks completely clean of film algae, hair algae, and even tough calcareous Coralline algae.

​The "Camouflage" Habit: These urchins are famous for picking up loose items from the substrate—such as empty snail shells, small loose coral frags, pebbles, and macroalgae—and wearing them on their backs using their tiny tube feet. While endearing, they are notorious for accidentally "stealing" unglued coral frags!

​Compact Size: Maxing out at a modest 2 to 3 inches in diameter, they are far more compact and agile than larger species like the Longspine or Pencil Urchin. This allows them to navigate tight rockwork formations without causing rockslides or bulldozing securely attached corals.

​Husbandry & Tank Setup

​🏠 Habitat Requirements

​An established aquarium with plenty of mature live rock is essential. The rockwork provides both a constant grazing ground for algae and the necessary structural stability, as these invertebrates can exert surprising strength when wedging themselves into crevices to rest during the day.

​🧪 Acclimation & Chemical Sensitivity

​Like all echinoderms, Tuxedo Urchins are incredibly sensitive to sudden changes in water chemistry, particularly salinity. Drip acclimation for at least 1 to 2 hours is highly recommended. Additionally, they have zero tolerance for copper-based medications or high nitrate levels, which can cause them to rapidly drop their spines—a primary sign of severe stress or impending mortality.

​🥬 Supplemental Feeding

​In pristine or low-nutrient systems, an urchin can easily exhaust its natural food supply. If the aquarium lacks visible algae growth, supplement their diet by placing a small strip of dried seaweed (Nori) underneath them, or allow them to crawl over a piece of algae wafer.

​Compatibility & Tankmates

​Fish & Invertebrates: They are entirely peaceful and pose no threat to fish, corals, or other cleanup crew invertebrates like snails and crabs.

​Predators to Avoid: Do not house them with aggressive fish species known to prey on invertebrates, such as large Triggers, predatory Wrasses, Puffers, or Hawkfish, which can flip the urchin over to attack its vulnerable underside.