Habitat
Imperators are found exclusively associated with coral reefs in the wild, in shallow to one hundred feet depths.
Chemical/Physical
Good water quality must be optimized and constant. use a good quality salt mix, at a 1.022-1.025 specific gravity and maintain pH in the higher range, 8.2-8.4. A protein skimmer is a must.
Angels are sensitive to "new tank syndromes". Place them in systems that have been seasoned for a few months.
Filtration
Very important to the group of angelfishes is vigorous circulation and removal of metabolites.
Display
Even in captivity emperors seek out/prefer the comfort of shelter from boulders, caves and coral niches. They will do well only where offered the possibility of retreat.
Size of aquaria? The bigger the better. I would not even start an emperor in a system of less than four hundred liters (roughly 105 usg). Ultimately, you will need one twice plus this size.
Behavior: Territoriality
Emperor angels are considered amongst the larger members of their family, able to reach some forty centimeters. Like most species in their and related genera, they do best kept singly and not with other angel species of a similar size.
Introduction/Acclimation
Place in a non-occupied or re-disturbed system in subdued lighting and leave some indirect light on for a day. Make favored foods available a few times a day at first.
Predator/Prey Relations
May be readily eaten by typical predaceous types. Beware of Billy Grouper, Eli the Eel, Larry the Langusto and Porky-boy the Puffer...
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
Similar to members of the genus Holacanthus, emperors and other Pomacanthus are known consumers of a large amount of sponge (phylum Porifera) material, then algae, other animal material and vascular plants in the wild. Will you go broke buying live sponges or specialty frozen foods made of the same? Nah. In captivity they can/usually will adapt/adopt to prepared frozen, fresh and dry foods.
http/www.wetwebmedia.com/marine/fishes/a...s/imperator.htm