Emperor angelfish, Pomacanthus imperator, are members of the family Pomacanthidae. The family Pomacanthidae encompasses all marine angelfish. There are seven cataloged genera and 86 species collectively referred to as saltwater angelfish. The are in no way related to the extremely popular freshwater angelfish species. Angelfish populate the shallow water reef formations in the tropical regions of the ocean. The emperor is indigenous to both the Indian and Pacific Oceans. Its habitat ranges from the Red Sea all the way to the shores of Hawaii and from Japan south to the Great Barrier Reef.

The Emperor is named for it regal color palette consisting of an electric, royal blue and bright yellow. The coloration of this species is distinctively different between adults and juveniles. When young, this species has a deep blue body color and tail fin. Contrasting dramatically against the dark body are concentric circles of black and white rings that expand very much like the ripples in still water when disturbed by a falling object. These circles begin it the tail region and work their way forward all the way to the fish’s head. At approximately four years of age the fish will undergo a morphological color change as part of its transition into adulthood. Adults have blue and yellow horizontal stripes across the length of their bodies, a black mask, rimmed in blue around their eyes and yellow as opposed to dark blue tail fins. Juveniles that are raised in captivity are generally not as vividly colored as their native counterparts. This may be due to a nutritional deficiency in captivity that is yet to be determined.

These are one of the more expensive saltwater species. You can expect to pay anywhere from $80 to upward of $300 dollars for one of these fish depending on its size and level of maturity. These fish are also marketed as Imperator (a commander in the Roman Legions) or Imperial Angelfish.

These angels are not recommended for the amateur saltwater aquarist. They are intolerant of anything less that pristine water conditions. They grow to an adult length of 15 inches. They require a minimum tank size of 100 gallons. They are also prone to parasite infestation. If you have a quarantine tank it is advisable to isolate them for a minimum of two weeks before introducing them to your other fish. If you buy one from a local retailer they may agree to quarantine it for you as part of the purchase arrangement.

These imperial angelfish are moderately aggressive animals. They tend to bully smaller fish and may very possible eat them. They should only be housed with similarly natured larger species. Emperor fish are extremely territorial toward members of their own species in the confines of captivity. You should not attempt to add more than one to your aquarium.

Even though they are native to tropical reefs, this species is not a suitable candidate for a marine reef aquarium. These fish will grow to be very large omnivores. They will readily devour the smaller crustaceans in your reef tank. And they will see both your soft and stony coral collection as a delicacy to be savored.

Remember this species is suspected to have a yet unidentified nutritional deficiency when raised in captivity. They should be fed a diverse diet simulating their dietary habits in nature as closely as possible. They will eat frozen marine foods, vitamin enriched brine shrimp, and marine algae. Their diet should be supplemented with chopped fresh seafood from your grocer regularly. Shrimp, mollusks, squid and octopus are recommended entrees. You can purchase marine foods especially developed for angelfish. They will include a percentage of sponge in the ingredients. Sponge is a primary source of nutrient for these fish in nature. It is strongly recommended that you thoroughly research this species' dietary requirements before you decide to make such a large expenditure.

Temperature	pH Level	Specific Gravity
72-78  °F	8.2-8-4	1.022-1.025