A Purple Tang.... also known as the Yellowtail Sailfin Tang, Yellowtail Surgeonfish, or the Blue Surgeonfish. is one of the most prized saltwater fish for its coloration, and are one of the most popular Tangs for the aquarium. Purple tangs grow to a maximum length of near 25 cm (9.8 in). Their bodies are purple in color with a yellow tail. The heads of purple tangs are covered with black spots, and black horizontal lines run down the sides of the bodies of some specimens. The center of their bodies are sometimes a darker color of purple relative to the rest of their bodies. On most specimens, the tips of their pectoral fins are yellow.
Like all members of the genus Zebrasoma, purple tangs have large dorsal and anal fins and an extended snout that is used to forage for algae within rocks. When the dorsal and anal fins are fully extended, the fish looks like a disk.
As typical of all surgeonfish, purple tangs have a sharp spines on each side of their caudal peduncle, which are used for defense.