Orange-shoulder Tang

Geographic Origin and Biotope: Resident in much of the Indo-Pacific (up to the Japanese and Hawaiian coasts). Compared to other tangs, it prefers sandy areas bordering the corals and moderately deep lagoon seabeds (up to 40 meters / 130 feet), where it "blows" and patrols the sand in search of diatoms.

Taxonomy and Morphology: Acanthuridae with a robust but slightly more slender body than its congeners. Characteristic for the pronounced convex profile of the snout in older specimens. Its caudal weapon is retractable. Reaches about 35 cm (14 inches) in adulthood.

Social Behavior: Emotionally much more peaceful, placid and balanced compared to the irascible Achilles, Lineatus or Sohal. Patrols the sandy bottom and tirelessly explores the tank without manifesting the frenzy typical of outer reef Tangs.

Coloration and Sexual Dimorphism: Stunning ontogenetic transformation. Juveniles are a dazzling monochromatic lemon yellow. Becoming adults, the livery mutates radically: anterior half ash gray or light beige, posterior half dark asphalt gray. The distinctive trait (Orange-shoulder) is a massive and unmistakable orange patch bordered with purple just behind the gill cover.

Aquarium Setup: Generous dimensions (at least 400-500 liters / 100-130 gallons, 150 cm / 5 feet side). It is essential to leave large squares of fine and clean coral sand on the bottom, which the fish will sift and graze continuously. Rocks arranged as an archipelago to allow long circular swims without blind obstacles.

Diet and Feeding: Pure detritivore and benthic herbivore. Sucks up the sand spitting it out to filter unicellular algae (diatoms, cyanobacteria) and small debris. Offer huge amounts of Nori algae tied near the bottom and sinking spirulina tablets. Abundantly supplement the diet.

Water Quality: Reef safe and on average resistant if well acclimated. Needs excellent biological filtration (powerful skimmer) to manage its impressive fecal waste. SG 1.023-1.025, stable pH 8.1-8.4, dKH 8-12. Does not tolerate ammonia spikes.

Compatibility and Tankmates: One of the most docile Tangs. Cohabits perfectly in community tanks with small quiet fish, angels and butterflyfish. Can be bullied by fiercer Tangs (Zebrasoma flavescens or Acanthurus sohal). Perfect for mixed coral tanks (SPS and LPS).

Aquarium Reproduction: Reproduction absent in the worldwide aquarium circuit. Like all Acanthurids, they are pelagic spawners that face an extended oceanic larval period before recruitment on the reef as bright yellow fry.

Risks and Diseases: Less prone to Ich than Leucosternon or Achilles, but remains equally susceptible during the acclimation phase. A peculiar risk is organic wasting due to poor feeding: without continuous access to plant food or mature sand to graze on, the abdomen will hollow out (pinched stomach) until death.