The handsome Emperor Angelfish is the best known of all the saltwater angelfish! Looking at the attached video of a juvenile in a 180 gallon, then the same fish 3 years later as an adult in 400 gallon tank shows how they reward their owners with great coloring in a properly sized tank!
The exotic Emperor Angelfish Pomacanthus imperator, also called the Imperator Angelfish or Imperial Angelfish, is one of the most recognized angelfish in the sea. It is unusually beautiful both as a juvenile and as an adult. Adults are truly regal, being deep bodied and slightly elongated with yellow and royal blue horizontal lines streaming across their frame.
Pictured above is the adult coloration of the Emperor Angelfish. Juveniles looks similar to the Koran Angelfish or Semicircle AngelfishPomacanthus semicirculatus. The pretty juveniles are black with light blue and white curved stripes and a honeycomb pattern on the top and bottom fin and tail made up of black spots edged in blue. The size of these angels when they start to change color is from 3 to 5” (8 – 12 cm). The best sized Emperor Angelfish to obtain for adjusting to life in a captive environment is a juvenile 4 to 6” (10 -14 cm) in length.
The Emperor Angelfish can reach up to 15.7” (40 cm) in the wild. In the aquarium however, they generally only grow to about 12” (30 cm). A minimum 125 gallons (473 l) will be needed for a juvenile, and 180 gallons (681 l) or more for a mated male/ female pair.. Make sure the tank is at least 6 months old, and has plenty of live rock for it to graze on. Several hiding areas will help it feels secure, so shape rocks into cave type formations as places of refuge and comfort.
In the aquarium the Emperor Angelfish are semi-aggressive, though they can be a good community fish with the proper tank mates, especially when young. As they grow, they start becoming contentious towards other angelfish and similarly shaped fish added later on. They should be kept singly as they do not tolerate their same species unless you have a mated male/female pair. Tank mates like cardinalfish, clownfish, and small peaceful fish will more than likely be harassed by an adult Imperial Angelfish. Adding the Imperator Angelfish last is the best choice due to their territorial behavior.
In a reef tank Imperator Angelfish will nip large polyp stony corals (LPS), anemones, zoanthids, clams and some soft corals. If you have a large tank with small polyp stony corals (SPS) and/or some noxious soft corals and the angel is well fed, they may leave them alone. Yet each Angelfish has its own idea of what “dinner” may be, and some may still pick at them.
For more Information on keeping saltwater fish see:
Marine Aquarium Basics: Guide to a Healthy Saltwater Aquarium
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Perciformes
- Family: Pomacanthidae
- Genus: Pomacanthus
- Species: imperator
- Aquarist Experience Level: Intermediate
- Aquarium Hardiness: Moderately hardy
- Minimum Tank Size: 125 gal (473 L)
- Size of fish – inches: 15.7 inches (39.88 cm)
- Temperament: Semi-aggressive
- Temperature: 72.0 to 82.0° F (22.2 to 27.8° C)
- Range ph: 8.1-8.4
- Diet Type: Omnivore
- My Aquarium – Enter your aquarium to see if this fish is compatible!
Habitat: Distribution / Background
The Emperor Angelfish Pomacanthus imperator , is also known as the Imperator Angelfish and Imperial Angelfish. It is from the Pomacanthidae family, and was first described by Bloch in 1787. Until 1933, juvenile Imperator’s were thought to be a separate species and called Pomacanthus nicobariensis.
The Imperial Angelfish is found in the Indo Pacific Ocean from the Red Sea and East Africa to the Hawaiian Islands, Line Islands and Tuamoto Islands. They can then be found from Southern Japan then south to the Great Barrier Reef, New Caledonia and Austral Islands. They are absent from the Easter Island, Rapa and Marquesan Islands. It is on the IUCN Red List as Least Concern (LC) with a stable population.
Juveniles inhabit areas under ledges or in holes of semi-protected channels, outer reef flats and outer lagoon patch reefs. The juvenile and sub-adult Emperor Angelfish have been seen cleaning larger fish in the wild. Subadults can be found in reef front holes and in surge channels. Adults are found under ledges and caves where there is plentiful coral, in seaward reefs, channels or clear lagoons.
Adults are generally found singly, but also occurs in pairs, trios, or harems of one male with two or more females. They are found at depths from 3 to 262 feet (1 to 80 m). Sponges, encrusting organisms and tunicates are their main food. As of yet, breeding in captivity is not possible and tank raising these angels has not been successful.
- Scientific Name: Pomacanthus imperator
- Social Grouping: Varies – Found singly, in pairs, in trios or harems of one male with two or more females.
- IUCN Red List: LC – Least Concern – Stable population.
The adult Emperor Angelfish or Imperator Angelfish are deep bodied and slightly elongated. They have yellow and blue horizontal lines throughout their body that start from just behind the gills to the area just before the tail fin which is yellow. Starting at the top of the dorsal fin to the anal fin, it is blue and can have some blue striping. The dorsal fin is trimmed in white.
The mouth and snout area are white, which is sharply cut off by a black mask that covers the eyes. The mask is black, trimmed in blue. There is a yellow vertical bar that extends from the yellow in the head downward. It divides the black mask from a thicker vertical black band that starts about 1/4 of the way down the body and continues down into the pelvic fins. This black band is in the same area of vertical space as the pectoral fins and gills.
Juvenile Emperor Angelfish are black with vertical lines in light blue and white on the face. Behind the gill area are 3 thicker white bands. The first is a curved band that starts from the dorsal fin to the anal fin, the second forms a “C” shape, and the third forms a white circle near the tail fin. In between these white bands are thinner light blue bands. The dorsal and anal fins have a honeycomb patterning that is black in the center and trimmed in light blue. The top dorsal fin has a white top edge.
Emperor Angelfish – juvenile
Emperor Angelfish – sub adult Photos © Animal-World
Sub-adult looks like the juvenile Emperor, except the tail fin starts to develop yellow in the patterning. Yellow vertical dashes start to appear on the body, blending into the juvenile pattern. The sub adult also becomes more deep bodied and rounder, like the adult.
Don’t confuse the Emperor Angelfish with the very similar looking juvenile Koran (Semicircle) Angelfish Pomacanthus semicirculatus. On a Koran juvenile, the very last white stripe makes a crude “C” shape that at times can form a circle. But the Imperator juvenile has a full circle within the “C” shape. The Imperator juvenile also has irregular light blue lined circles in the dorsal and anal fin, where the Koran does not.
The Imperator Angelfish are deep bodied and can grow up to 15.7” (40 cm) in the wild, yet in captivity, they will generally only reach about 12” (30 cm). Angelfish from the Pomacanthus genus have a lifespan of over 21 years in captivity.
- Size of fish – inches: 15.7 inches (39.88 cm) – In captivity, they will generally only reach about 12” (30 cm).
- Lifespan: 21 years – Pomacanthus can have a lifespan of over 21 years in captivity.
Fish Keeping Difficulty
The Emperor Angelfish are considered moderately hard to advanced in difficulty because of the excellent water quality that is needed. A large tank with numerous caves is also needed to properly house this fish. A tank that is at least 135 gallons (378 l) is needed for a single specimen, but a tank of 180 gallons (681 l) or more can lower stress levels as well as house a male/female pair.
When obtaining your Emperor Angelfish, the best size for adjusting to life in a captive environment is 4” to 6” (10-14 cm) in length. Make sure they are very curious and active in their environment. Although they usually begin to change to their adult coloration from 3 to 5” (8 – 12 cm) in length, this is often delayed in captivity. In the aquarium they also do not always attain the same level of brilliance as specimens found in the wild. Color enhancers in their food may help.
If an Emperor Angelfish is disoriented and excessively bright, that can be a sign that they are victims of cyanide and will die. Also, a gill count of over 80 a minute as they calmly swim around is a red flag. It is very important to direct the fish into a container or bag to capture it, since nets can get snagged on their gill cover spines. This can cause injury which can lead to possible infection and subsequent death.
- Aquarium Hardiness: Moderately hardy
- Aquarist Experience Level: Intermediate
Foods and Feeding
Emperor Angelfish are omnivores, in the wild they eat a wide variety of sponges and encrusting organisms along with small amounts of algae, tunicates, hydroids, and bryozoans. It is important that you feed angelfish all kinds of live, frozen, and prepared formula foods. Feed vegetable based foods as well as meaty foods like chopped squid, scallop, and shrimp. Prepared foods with marine sponge and tunicates are essential. Foods containing color enhancing qualities may be used as well. A good formula that can be made at home consists of mussels, shrimp, squid, and spinach. Feed 2 to 3 times a day in smaller amounts to keep water quality good.
- Diet Type: Omnivore
- Flake Food: Yes – With spirulina and sponge material included, and color enhancing foods are also helpful.
- Tablet / Pellet: Yes – With spirulina and sponge material included.
- Live foods (fishes, shrimps, worms): Some of Diet – Brine shrimp, mysis shrimp, as well as other protein sources can be offered occasionally.
- Vegetable Food: Some of Diet
- Meaty Food: Some of Diet
- Feeding Frequency: Several feedings per day – They need 2 to 3 feedings a day that includes vegetable matter, sponge material, and meaty foods.
In general, Pomacanthus angelfish are not as forgiving as many other fish when it comes to water quality. Water quality must be high for the Imperial Angelfish to prevent illness, which can lead to death. Water changes of 30% a month, or 15% every 2 weeks is optimal in keeping nitrates lower. If there are corals in the tank, then 20% every month, 10% every 2 weeks or 5% a week works great.
A large tank is important for this large fish. Because it needs a lot of food, there is a large bio-load on the aquarium and a smaller tank will foul quickly. A suggested guideline is to keep up with your water testing, which will tell you when your tank needs a water change.
- Water Changes: Bi-weekly – Water changes of 15% every 2 weeks or 30% a month. If there are corals in the tank, then 10% every 2 weeks or 20% every month.
The Emperor Angelfish, like other large angelfish, needs a stable environment which is at least 6 months old. It is best to introduce it last as a young fish into an established tank. A minimum 125 gallons (473 liters) will be needed for a juvenile, and a of tank of 180 gallons (681 l) or more for a mated male/ female pair.
Like others angelfish, they enjoy large amounts of rock work to graze on and for refuge. Arrange the rockwork in a way that your Imperator Angelfish can “hide” when needed. Provide water parameters of: 72-82° F, pH 8.1-8.4, sg 1.023-1.025. While seen as brightly colored fish in books and online, it has been stated that they may end up in a more faded version if a juvenile coloration is acquired and raised in captivity. It is possible that this is due to the lack of lighting in a fish only tank. It may be that providing reef lighting as you would for corals, may help. A decent amount of lighting has also been observed to help other Pomacanthus from developing HLLE (Head and Lateral Line Erosion Disease).
- Minimum Tank Size: 125 gal (473 L) – A tank that is 180 gallons (681 l) or more is needed to keep a male/female mated pair.
- Suitable for Nano Tank: No
- Live Rock Requirement: Typical Plus Hiding Places – Hiding places are needed to help reduce stress.
- Substrate Type: Any
- Lighting Needs: Any – These angelfish also need decent reef-like lighting or they can develop HLLE (Head and Lateral Line Erosion Disease).
- Temperature: 72.0 to 82.0° F (22.2 to 27.8° C)
- Specific gravity: 1.023-1.025 SG
- Range ph: 8.1-8.4
- Brackish: No
- Water Movement: Any – It can tolerate a rather stronger flow but slow-moving water is preferable.
- Water Region: All – They will spend time in all parts of the aquarium.
In the wild they are found singly, in pairs, in a trio or harem of one male and two or more females. They are generally peaceful in the aquarium but can be aggressive towards other Emperor Angelfish and other large angelfish species. They will harass smaller fish like gobies, clownfish and blennies. Because they establish territories that they will defend, they should be the last fish you introduce into the tank. An adult may be okay with a juvenile of the same species until the color change, at which time the adult would become intolerant. Slower moving sharks and stingray, especially their eyes, may be picked by larger angelfish.
In a reef environment they will eat at Large Polyp Stony Corals (LPS), most soft corals, Zoanthids, and Tridacnid clams. Use caution with Small Polyp Stony Corals (SPS), even SPS corals are not always safe from these coral carnivores. They may be a threat to small decorative shrimp as well.
- Venomous: No
- Temperament: Semi-aggressive
- Compatible with:
- Same species – conspecifics: No – Only as an adult with a juvenile until the young fish changes color, or as male/female mated pair.
- Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Monitor – May pester very passive fish.
- Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor – May be aggressive towards clownfish and dwarf angelfish.
- Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Will be aggressive towards other large angelfish species.
- Large Aggressive, Predatory (lionfish, groupers, soapfish): Monitor – Slower moving sharks and stingray, especially their eyes, may be picked by larger angelfish.
- Threat – Angelfish are too aggressive in feeding to keep with slow feeding species.
- Anemones: Monitor – May nip at them.
- Mushroom Anemones – Corallimorphs: Monitor – May nip at them.
- LPS corals: Threat
- SPS corals: Safe
- Gorgonians, Sea Fans: Threat
- Leather Corals: Threat
- Soft Corals (xenias, tree corals): Safe
- Star Polyps, Organ Pipe Coral: Monitor
- Zoanthids – Button Polyps, Sea Mats: Monitor
- Sponges, Tunicates: Threat
- Shrimps, Crabs, Snails: Monitor – May be a threat to small decorative shrimp.
- Starfish: Safe
- Feather Dusters, Bristle Worms, Flatworms: Monitor
- Clams, Scallops, Oysters: Threat
- Copepods, Amphipods, Mini Brittle Stars: Safe
Sex: Sexual differences
It has been stated that the blue in front of the eye mask is more blue in male Emperor Angels, and gray blue in females.
Breeding / Reproduction
As of yet, breeding in captivity is not possible and tank raising these angels has not been successful. Successful breeding can only be accomplished in a very large display aquarium. Most home aquarists will not have a tank large enough to encourage spawning with this angelfish.
The Emperor Angelfish pair will spawn once a year. In the Marshall Islands, they spawn August and September. Males will have 2 or more females in their harem, with each female having their own territory. It is possible, like other Pomacanthus , that they ascend in the water column, circle each other and simultaneously release their sperm and eggs at the pinnacle of their accent. The larvae float in a planktonic stage for a few weeks before turning into fry. The males are known to “grunt” as they descend from spawning.
See Breeding Marine Fish for a description of how they reproduce in the wild.
- Ease of Breeding: Difficult
Emperor Angelfish, like other saltwater angelfish, are prone to any disease that captive saltwater environments have to offer. They are most likely to be affected if they are stressed from inappropriate housing or tank mates. This angelfish may suffer from Saltwater Ich or White Spot Disease (Crypt) and other infectious diseases.
White Spot Disease Cryptocaryon irritans, also known as Marine Ich, Saltwater Ich, or Crypt is the most common disease that is generally associated with marine tangs and angelfish. Symptoms of Marine Ick are constant scratching, culminating with lots of white dots. These dots disappear for a few days, only to return with double the number. This results in the fish suffocating from these parasites blocking the gills from providing oxygen.
Another common disease is Marine Velvet or Velvet Disease Oodinium ocellatum, (syn: Amyloodinium ocellatum or Branchiophilus maris), which is a parasitic skin flagellate. Symptoms of Marine Velvet are a peppery coating giving a yellow to light brown “dust” on body, clamped fins, respiratory distress (breathing hard as seen as frequent or quick gill movements), cloudiness of eyes, glancing off decor or substrate, and possible weight loss.
Parasites on marine fish kept with live rock or in any type of reef environment can be extremely difficult to treat. Typical treatments like copper and formalin solutions, as well as quinine based drugs are harmful to other marine creatures. However drugs such as metronidazole provide an effective and safe treatment for several protozoan and anaerobic bacterial diseases. Metronidazole works by ceasing the growth of bacteria and protozoa. Metronidazole is an antibiotic for anaerobic bacteria with anti-protozoal properties. This drug is reef safe, and medications are either added to the water or mixed with the fish food. Some available products that contain metronidazole include Seachem Metronidazole, Seachem AquaZole, Thomas Laboratories’ Fish Zole and National Fish Pharmaceutical’s Metro-Pro.
For external parasites you can slowly increasing the temperature of your tank to at least 82° F (28° C). That will prevent the parasite from completing its life cycle which includes the attachment to fish. A further combination of the higher temperatures with medicated food will provide timely relief. The Seachem Metronidazole medications works well in combination with another Seachem product called Focus, which is a bonding agent. This treatment can be used in a reef aquarium since the medication is bound to the food, which even if the corals eat, will not hurt them. Mix Focus in a ratio of 5 to 1 with their Metronidazole (5 parts Focus to one part Metro), then mix this with 1 tablespoon of food. Feed the medicated food to the fish 3 times a day for at least a week or until symptoms are gone.
For more information on diseases that saltwater angelfish are susceptible to, see Aquarium Fish Diseases and Treatments.
The Emperor Angelfish or Imperator Angelfish is moderately easy to find online and in stores, but rather expensive.
- Animal-World References: Marine and Reef
- Pomacanthus imperator (Bloch, 1787) Emperor angelfish, Fishbase
- Pomacanthus imperator, IUNC Red List, International Union for Conservation of Nature and Natural Resources
- Helmut Debelius and Rudie H. Kuiter, World Atlas of Marine Fishes, (in German) Hollywood Import & Export, Inc., 2006
- Scott W. Michael, Angelfishes & Butterflyfishes: Reef Fishes Series , Microcosm Ltd, 2004
- Scott W. Michael, Marine Fishes: 500+ Essential-To-Know Aquarium Species, T.F.H Publications inc., 1999
- Mark Allen, Roger Steene and Gerald R. Allen, A Guide to Angelfishes and Butterflyfishes , Odyssey Publishing, 1998
- Dr. Gerald R. Allen, Butterfly and Angelfishes of the World Volume 2, Aquarium Systems; 3rd edition,1985