Atlantic Blue Tang (Acanthurus Coeruleus)

Also Known As: Atlantic Blue Surgeonfish

Compatibility and Behavior
Few tangs reinvent themselves as completely as the Atlantic Blue Tang (Acanthurus coeruleus). It starts life as a rich golden-yellow to mustard youngster, compact and bright, then over time trades that color for the electric-to-deep-cobalt blue it is named for, often finishing with a slightly lighter face and subtle fin edging that glows under reef lighting. Watching one make that journey from yellow juvenile to bold blue adult is one of the genuine pleasures of keeping this species, and it is a big part of why reefers seek them out small. Temperament tends toward the assertive end of the surgeonfish range, generally semi-aggressive and willing to throw its weight around with other tangs and similarly shaped grazers, especially in smaller or crowded systems. It is reef safe in the practical sense, spending its day grazing film and filamentous algae off rock and hard surfaces rather than picking at corals or inverts, though a stressed or underfed individual may occasionally nip. Give it the space it wants and it usually becomes one of the more outgoing, front-and-center fish in the display.

Aquarium Requirements
This is an active, medium-sized tang that wants horizontal room to cruise and a mature system with well-established live rock to graze. For small to medium specimens in the 1.5 to 3 inch range, a tank around 90 to 120 gallons with a long footprint is a sensible baseline, with larger systems preferred as it grows and for long-term comfort. Aquascape with open swimming lanes alongside sturdy arches and ledges where the fish can wedge in at night or when startled, on porous rock that keeps the algae and biofilm coming. The rest is standard tang care: strong, well-oxygenated flow, robust filtration, and stable water quality. Keep nori, marine algae, and quality herbivore foods in steady rotation to maintain health, support that yellow-to-blue transition, and take the edge off its more territorial moments.

Specifications
Approximate Size: Sm: 1.5–2", Md: 2–3", Lg: 3–4"
Diet: Herbivore; marine algae, nori, spirulina-based prepared foods, with supplemental quality pellets and frozen fare
Origin: Western Atlantic and Caribbean
Care Level: Intermediate
Reef Safe: Yes
Temperament: Semi-aggressive
Minimum Tank Size: 90 gallons for small specimens, with a larger system required as it grows
Special Considerations: Dramatic color change from yellow juvenile to cobalt-blue adult; tends to be more assertive than many tangs and may be territorial toward other tangs and similarly shaped grazers