Achilles Tang Identification Guide

Key identification features

• Deep, oval, laterally compressed body covered in velvety black
• Large orange-red teardrop patch surrounding the white scalpel-like spine on the tail base
• Thin orange line tracing the edges of the dorsal and anal fins, sometimes with a fine blue border as well
• Crescent-shaped (sickle) tail fin, often with an orange tint along its trailing edge
• Adults typically reach 18-24 cm with a small terminal mouth adapted for grazing algae from rock and coral
• Juveniles are similarly dark but show a less developed, smaller orange tail patch that intensifies with age

Common look-alikes

• Powder brown tang (Acanthurus japonicus): similar black-brown body, but has a white patch near the mouth and cheek rather than an orange teardrop at the tail base
• Convict tang: black-and-white vertically barred body, lacking any orange coloration at all
• Whitecheek surgeonfish: shows a pale cheek patch instead of the orange tail marking that defines the Achilles tang

Where you'll see one

Inhabits high-energy, surge-swept outer reef edges, tide pools, and rocky shorelines across the tropical Pacific, usually alone or in small loose groups grazing algae from wave-washed rock and coral in shallow water.