The emperor angelfish (Pomacanthus imperator) has to be one of the most stunning fish you could encounter underwater. The emperor angelfish’s color, graceful shape and stately disposition will cause the most jaded divers or aquarists to stop what they are doing, so they can admire it as it swims past. While the emperor angelfish can make a fantastic display fish, it can also cause much consternation for the less experienced or unlucky fishkeeper.
Difficulty: The emperor angelfish can vary in its durability in captivity. Adult emperor angelfish will definitely have a more difficult time acclimating than juvenile emperor angelfish. In most cases, the larger fish will be more reluctant to accept captive foods, though with some patience (and if water quality and tankmates are not a problem), it usually will eat foods like frozen mysid shrimp and finely chopped seafood (e.g., shrimp, scallop). Juvenile emperor angelfish tend to be less finicky, feeding on most available fish foods (some will not eat flakes). Feed the emperor angelfish one to three times a day, depending on if there is natural fodder available for it (e.g., algae, sponges).
Physical description: The color of the juvenile P. imperator and the adult are very different. The juvenile emperor angelfish is dark blue overall with concentric white circles on the body and lines on the head. The adult emperor angelfish is yellowish-green with blue lines on the body and a black eye bar and chest shield. Pomacanthus imperator males have a blue face (in front of the eye band), while in females, this area is gray. As a juvenile emperor angelfish grows, it begins taking on some of the markings of the adult, which gradually replace all the juvenile color characteristics. In captivity, this metamorphosis can occur earlier than it would in the wild, and the final adult coloration may not be as splendid as that seen in a wild-caught adult emperor angelfish. The size at which ones of these fish totally changes can vary greatly, but the smallest adult emperor angelfish measure about 4 inches in length. The emperor angelfish attains a maximum length of 15 inches.
Range: The emperor angelfish is known from the east coast of Africa and the Red Sea east to the Hawaiian Islands (it is rare at this location). The emperor angelfish makes its home on lagoon patch reefs, reef faces, channels and fore reef slopes at depths of 10 to 260 feet. The juvenile emperor angelfish often hang out under ledges or near the mouth of caves, while adult emperor angelfish are more often seen patrolling over the open reef. Juvenile emperor angelfish occasionally clean other fish and may specialize in picking at large moray eels. The adult male P. emperor defends a large territory that is home to two or more female emperor angelfish. The primary foods of the adult emperor angelfish are sponges and tunicates.
Compatibility: A juvenile emperor angelfish is unlikely to cause behavioral problems in the home aquarium — unless it is kept with another young emperor angelfish or a juvenile angelfish with a similar color pattern (there are many Pomacanthus from the Indo-Pacific that have the same general dark bluish to black body with white and light blue markings). The young emperor angelfish does not usually catalyze attacks from fish, with the exception of similar angelfish. However, the emperor angelfish may occasionally be chased off by territorial, benthic species, like dottybacks, hawkfish and damselfish (including larger anemonefishes). Adult emperor angelfish have been known to spar with other angelfish, surgeonfish and triggerfish. One thing that will decrease the likelihood of an adult emperor angelfish acclimating is it being pestered by reef bullies. That said, once the emperor angelfish has fully established itself in an aquarium, it may become a bit of a rogue itself. The emperor angelfish is most likely to chase butterflyfish and other angelfish. If an aquarium is large enough (e.g., 240 gallons or more), it is possible to keep a juvenile emperor angelfish with an adult emperor angelfish. However, as the young emperor angelfish begins transforming into the adult colors, the larger fish may begin to attack it. The emperor angelfish is a protogynous hermaphrodite.
Aquarium conditions: When it comes to the adult emperor angelfish, the bigger the aquarium, the better. An aquarium of at least 135 gallons is recommended for an adult emperor angelfish, and a more voluminous aquarium would make life for your emperor angelfish optimal. It is important to provide your emperor angelfish with good hiding places to dash into when it is frightened. Keep the water parameters for the emperor angelfish in the following ranges: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 76 to 82 degrees Fahrenheit.
Care considerations: It is advisable to stay away from emperor angelfish that are either tiny or “show-sized.” You are better off going for the larger juvenile and the subadult or small adult emperor angelfish, as these tend to acclimate more readily to captive living.
Breeding: The emperor angelfish is not likely to spawn in the home aquarium.