The members of the family Pomacanthidae are generally know as angelfishes and, like their nearest cousins, the butterflyfishes, are regarded by many divers and aquarists as being amongst the most beautiful and majestic fishes in the sea. The majority of species occur on shallow reefs in coral, algae and sponge zones, most going little deeper than about 30m but where conditions are pristine and water is very clear, many species go much deeper and few species only live deep (over 100m). Angelfishes feature a large and distinctive backward-protruding spine from the lower corner of the gill-plate (cheek spine) from which the family name was derived. This cheek-spine is diagnostic for all the species , even at juvenile stage, and readily separates any angelfishes from butterflyfishes that may be similar in shape. Mot angelfishes are robust with compressed, ovate to rhomboid shaped bodies, covered with small or tiny scales, and have a continuous dorsal fin. The mouth is small and jaws are set with many small, usually tricuspid teeth that are used for grazing algae or scraping sponges and other sessile invertebrates. Few species combine their diet with a variety of foods and some are planktivores.
Throughout the Red Sea to the western tip of the Arabian(Persian) Gulf, and ranges southward to the coasts of Somalia and Kenya. Mainly occurs on sandy or coral rich reefs, shallow depths to at least 60m. The yellow-blotch angelfish lives solitary, establishing large territories in fringing reefs, which are constantly patrolled. A large and impressive angelfish due to its shape and colour. Adults usually pale blue with a large yellow blotch on their side. Small juvenile P.maculosus have alternating white and light blue vertical lines on a dark background, and are distinguished from the similar juvenile P.asfur by their paler caudal fin and more rounded anal fin, but the caudal fin may also turn bright yellow at some stage. Changes from juvenile to adult patterns occur at a length of about 10cm. Can reach 50cm, usually to about 35cm.