Blue-ringed angelfish, also known as shoulder ring hedgehog, ring-striped angelfish, is a genus of caps in the family Butterflyfish of the order Perciformes. It is a warm-water coral reef fish with a body length of about 30 cm, which is the larger of the spiny fish. It is found in the Indian Ocean and the western Pacific Ocean between the Tropic of Cancer, and China is found in the Paracel Islands and the Taiwan Strait. It inhabits seafloor rocks, coral reefs and other offshore areas with hard bottoms at depths of 5–15 m.
The body is slightly tall and ovoid , the dorsal contour is slightly prominent , and the dorsal part of the head is straight above the eyes. The posterior and lower margins of the anterior gill cap are weakly serrated and have a long spine. Adults are yellowish-brown or greyish brown with multiple ring-shaped bands on the side of the body that extend through the body side to the back of the dorsal fin. Two similar horizontal blue stripes sweep across the face. Above the gill cap, at the front of the lateral line, there is another blue ring about the diameter of the eye. The dorsal and fins are softly striped and dark, with blue stripes; The caudal fin is white mixed with bright yellow edges.
Juveniles and adults differ greatly in body color. Juveniles are orange-red to reddish-brown , with 3-5 dark blue arcs streaks slanting from the base of the pectoral fin upwards to the soft stripes of the dorsal fin , and several crescent-shaped narrow white transverse bands on the side of the body. Juveniles live above the adult water layer, in shallow waters with brachyphyllous algae or sedimentary coral substrates. Blue-ringed angelfish are omnivorous fish that feed on plankton, sponges, algae and polyps. They gather in seabed caves in pairs at night and forage alone or in pairs during the day.