The Emperor Angelfish, known by the scientific name pomacanthus imperator is a reef-associated fish that is found in some saltwater marine aquariums. In the wild, its range is vast and can be found along the shores of Africa, Hawaii, the Equatorial Islands, French Polynesia, Japan and Australia, among other places. The emperor fish is known for its striking appearance.
Juvenile members of the species are dark blue, sometimes black, with white circles covering the body and fins. When it reaches adulthood, the fish's coloration changes dramatically. The blue coloration fades to a lighter color and the circular pattern is replaces by a series of thin yellow stripes that cover its entire body. The caudal fin is often completely yellow, and the snout is entirely with a black bar covering its eyes.
In the wild, the emperor angelfish is usually found in areas where algae is plentiful, such as a reef or lagoon. When not eating it will usually reside in rock crevices, in caves or under small ledges to protect themselves from larger predators. The depth range for this fish can vary, with fish being found anywhere from surface level to 330 feet (100 meters) deep.
The emperor angelfish is a popular fish for marine aquarium enthusiasts, but it is not an easy fish to keep. Beginner marine aquarists are usually advised against keeping them. Unlike many other types of fish, the emperor angelfish can only survive in very specific water conditions. The water temperature can only be between 73 and 78 degrees Fahrenheit (22 to 22.5 Celsius), and the pH range is extremely narrow at 8.2 to 8.4. It will nip and possibly damage aquarium reefs, so care must be used when choosing hidings spots and decorative features.
It is also a somewhat aggressive fish. Emperor angelfish will attack members of its own species. Other kinds of non-aggressive fish can be good tank mates, assuming they are added to the tank before the emperor. Regardless of what the emperor shares the tank with, the tank must have plenty of natural rocks that include deep cracks and caves for the angelfish to feel comfortable. It also needs to be a very large tank, 100 gallons (375 liters) is an advised minimum size by many fish experts. A full-sized adult emperor angelfish would probably need a 200 gallon (750 liter) aquarium to be comfortable. Anyone looking to buy an emperor angelfish should also be aware of the cost as this is an expensive fish when found at a retail outlet.