The adult Emperor Angelfish, also called the Imperator Angelfish, has a bold, blue body covered with bright yellow horizontal stripes culminating in a bright yellow to orange caudal fin. A striking blue-black mask covers the eyes and a similarly-colored vertical band extends from the pectoral fin two-thirds of the way up the body. This band is highlighted in a sapphire-blue in front, and bright yellow, caudally. The mouth is white.

The juvenile is black with circular white and blue stripes starting at the tail. Although sought after for its colors, in captivity, the adult coloration may not be as striking or brilliant. The changing angelfish will vary in coloration and pattern as it transforms from juvenile to the adult coloration.

The Emperor Angelfish requires a 220 gallon or larger tank with live rock for grazing and hiding. They also require extensive rockwork and deep caves to feel secure. It will nip at stony and soft corals (sessile invertebrates) and clam mantles, but may be kept with small-polyped stony corals and somewhat noxious soft corals.
It should be fed a diet of Spirulina, marine algae, high-quality angelfish preparations, mysis or frozen shrimp, and other meaty items.