Marine angelfish are perciform fish of the family Pomacanthidae . They are found on shallow reefs in the tropical Atlantic , Indian , and mostly western Pacific oceans. The family contains seven genera and approximately 86 species. They should not be confused with the freshwater angelfish , tropical cichlids of the Amazon River basin. With their vibrant colours and deep, laterally compressed bodies, marine angelfishes are some of the more conspicuous residents of the reef. They most closely resemble the butterflyfishes , a related family of similarly showy reef fish. Marine angelfish are distinguished from butterflyfish by the presence of strong preopercle spines (part of the gill covers) in the former. This feature also explains the family name Pomacanthidae; from the Greek poma meaning "cover" and akantha meaning "thorn“.