Emperor Angelfish – A Complete Guide (Care, Diet, Facts)

For experienced saltwater tank owners, the appeal of a fish may lie in both the physical appearance of the fish, and in the reputation it may have among other aquarium keepers. The Emperor Angelfish is one such fish, with a captivating color pattern, curious personality, and tank care requirements that make it for experts only.

The Emperor, or Imperator, Angelfish, belongs to a family of marine fish that includes both other Angelfish species, as well as butterfly fish. Adults are large, and can reach over 15 inches in length.

It is known for more than its size, however. The Emperor Angelfish is among the most vividly colored and patterned aquarium fish available. High demand among aquarium keepers led to high prices, but global supplies have made these fish more affordable, and can be found for $60-75 at most pet stores.

Their size and territorial tendencies mean that large tanks are a requirement for successful ownership. This and other aspects of ownership will be discussed throughout this article.


The Emperor in the Wild

The emperor angelfish, known also as the Imperator or Imperial Angelfish, is a reef-dwelling marine fish, desired by aquarium owners for its distinct, vivid colorings. It is native to the warm, tropical waters of the Indian and Pacific Oceans. The wild population of this fish is under no threat of endangerment, giving peace of mind to potential owners.

In some extreme locations where the fish has been sighted in the wild, such as Japan and Florida, it is suspected that this is due to them being released by salt-water tank owners. This is highly discouraged, as it can both stress the individual fish, and alter the local marine ecosystem.

Emperor Angelfish are found at varying water depths throughout reef environments, generally corresponding to their age. Juveniles inhabit shallower areas, where they are out of reach from larger predators. At a sub-adult stage, the fish move towards the edges of reefs, looking for areas to both hide and feed.

Adults can be found at depths of 100 m beneath the surface, looking for deep caves and ledges, but also swimming in open waters at times to patrol their territory. Males in particular are highly territorial, and are known to attack species larger than themselves, including humans diving within their boundaries.

These territories can span up 10,000 square feet, and may give some idea of the tank size necessary to successfully own one of these fish. Angelfish territories will encompass a variety of live rock, coral formations, and marine plant-life. These serve to provide them both with shelter and feeding grounds.

Life Cycles

The Emperor Angelfish passes through three distinct stages during its life. As a juvenile, it inhabits shallower waters, such as lagoons, inlets, and edges of channels. This allows it to feed with relative safety. At this stage of its life, the angelfish is not nearly as territorial as its adult counterpart, and can tolerate others of its kind.

The array of colors and patterns on the juvenile Emperor Angelfish is drastically different array from the adult. The rear of their body features a series of expanding rings in black, white, and blue. The front half features vertical bands of the same colors that sweep back towards the tail. Their dorsal and anal fin feature spots of electric blue and deep black, and these fins also appear fringed at the edge.

Their appearance is so distinct from adult emperor angelfish that until 1933, scientists categorized juveniles as a separate species. They may retain this coloration until they reach 5” in length. Some will begin to shift colors at 3” in length, however.

Sub-Adult and Adult Stage

As the fish enters the sub-adult stage, the color patterns change. In the back half of the body, the whites and blues give way to a rich yellow, and horizontal lines begin to appear at the pectoral fin. Black is more prominent towards the head, and the spots on the dorsal and anal fin shrink. The fringes begin to disappear on the fins as well. Around the mouth, the scales turn to an ivory or white color, and the face will elongate.

They can often be seen cleaning other fish as juveniles and sub-adults,. Some will exhibit this behavior in home aquariums, depending on the variety of fish around them. This is a fun and unique behavior to observe. Adults are known to act as cleaners occasionally for much larger fish, but they will be the largest individuals in most tanks, so this is rare outside of the wild.

As the emperor angelfish reaches 6 inches in length, it enters its adult stage. The body becomes deeper and more elongated. Its body is characterized by blue and yellow stripes that sweep horizontally along the body. The tail fin lengthens and separates from the anal and dorsal fin, and is now solid yellow. The anal fin is striped with black and electric blue.

The mouth is white, and a solid black mask stretches across its eyes. This mask sweeps down to the pectoral fin, almost looking like a strap. From the pectoral fin, the strap widens again, and reaches vertically above the fin and gills. These black sections on the fore of the body are edged with electric blue.

The adult is a striking fish, almost dramatic in appearance. From the 6 inches in length at which its colors will start to shift, it may grow to be as large as 16 inches, depending on the size of your tank. It is an active swimmer, and will be highly visible in any aquarium setup.


The Emperor Angelfish is a highly omnivorous and opportunistic feeder. In the wild, they will eat a variety of invertebrates, including sponges, worms, anemone, and small shrimp and crabs. They also nibble on loose algae, coral growths, and other plant matter, and will also feed on zooplankton and phytoplankton as it drifts into their reef territory.

For home aquarium owners, this means providing a balanced diet that mimics the variety of food the angelfish eats in the wild. When purchasing food at pet supply stores, carefully check the ingredients. Flaked food and pellet food is acceptable, provided it has spirulina and sponge matter. Live food might include brine shrimp, mysis shrimp and other small invertebrates.

Emperor Angelfish may pick at algae that grows in your tank, so be sure to provide live rock that can sustain algae at a steady rate. Algae can also be mixed into their food supply. Meaty formula feed that include shrimp, octopus, shellfish, and plant matter can be included as well.

Vitamin-enhanced food is recommended by experts. This will not only help the fish to maintain its health, but will also enhance the vibrancy of its colors. There are reports of juveniles in captivity not developing their adult coloration due to insufficient diets. This can easily be avoided by feeding your fish 2-3 times a day, and providing it with a variety of choices. The angelfish may be picky, depending on its mood, but a healthy individual will almost always be interested in feeding.

Tank Care

The Emperor Angelfish is a fairly robust specimen, and with proper care, often lives in captivity for 12-13 years. It is more sensitive than other species to water quality, however, another reason that owners should be experienced in salt-water tank maintenance.

A tank size of at least 125 gallons is recommended. This provides the fish enough room to establish a territory, navigate the water column, and swim freely through the terrain that you provide.

A single fish is all that most owners should try to accomodate. They are solitary fish in the wild, and two emperor angelfish would likely fight, and possibly inflict mortal wounds upon each other. Ambitious owners may want to keep a male and female pair together, however. In this case, the fish will need a tank size of at least 180 gallons.

Emperor angelfish feed often, and in large amounts. This means that waste will accumulate, and water may foul quickly with left-over food and organic waste. Plan on changing out 30% of the water each month. This can be done all at once, or by refreshing 15% of the tank’s volume every two weeks.

Tank Setup

Live coral will help to keep water fresh, and reduce the impact of frequent feeding on the water quality. The angelfish will nibble on the coral however, so be sure to select a species of coral with a high growth rate. They are not considered coral safe, and large polyp stony corals are most vulnerable to their grazing habits. Small polyp coral species are more likely to withstand the Emperor Angelfish’s appetites.

A variety of live rocks should be included in their tank to replicate the reefs they would swim through in the wild. These should include hiding places like caves, holes, tunnels and ledges, all of which help to minimize stress on the fish.

They enjoy a water temperature between 72-80 degrees fahrenheit, or 22.2 – 27 celsius. While capable of withstanding slightly higher or lower temperatures, it is not ideal, and may leave them susceptible to disease or parasitic infection.

Keep a pH range between 8.1 – 8.4, which is fairly typical for most saltwater tanks. A gravity of 1.023 – 1.025 is suitable for the emperor angelfish, which is a slightly tighter requirement than other salt-water fish will need.

Strong reef lighting is recommended, as dim or insufficient light may prevent the fish from developing properly, and may even result in a condition known as Head and Lateral Line Erosion Disease (HLLE).

Tank Mates

The Emperor Angelfish is territorial, semi-aggressive, and ill-suited to coexist with its own kind. Whether you are creating a new tank with the angelfish as a focal point, or adding it to a large tank you already own, be cautious of how it interacts with other species.

Not only does it view others of its species as threats, if a fish has similar colors, or a similar approximate shape, the angelfish may attack. This includes other angelfish species, even smaller ones.

Slow-moving fish may be picked on by the angelfish, including sharks and rays. Seahorses and pipefish may also bothered, and because they are slow feeders, the Emperor Angelfish may crowd them out. Passive and peaceful fish will also be harassed, and should not be kept with the Emperor Angelfish. Semi-aggressive species, such as clownfish, may still need to be monitored.

Aggressive marine species with distinct body shapes will fare best with the Emperor Angelfish. This includes wrasses and damselfish. They will likely prey on invertebrate species, especially decorative shrimp.

Due to its aggressive, territorial nature, consider introducing it as a juvenile to your tank, and as one of the final species you add. This will allow the other fish to have some comfort in establishing their presence and holding their ground against the Emperor Angelfish.

The Emperor Angelfish has its challenges, and is recommended for experienced marine aquarium owners only. For many, however, this may be part of its lure. It is undeniably beautiful throughout all stages of its life. Its bold personality and exclusivity are also sure to hold an appeal for many. WIth proper care and tank setup, it is a long-lived fish, and should provide an attentive owner with years of enjoyment.

Regular feeding and a properly selected diet are a requirement, as is good lighting, a large volume tank, and regular cycling of its water.

Expect to pay at least $60 for your fish. Prices may vary based upon where the fish are from. Colors and patterns will differ subtly depending on where the fish was raised (ie Australia, Japan, India, etc), and some varieties will command a higher price.

Owners who are prepared for the task of keeping the Emperor Angelfish will find them rewarding to care for. Their curious ways and high levels of activity will attract attention from fish enthusiasts and novices alike. It is also a treat to watch them grow and change throughout their life cycle.

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