The Three-spot Angelfish is bold in color and peaceful in demeanor, but difficult to keep long term!

The Flagfin Angelfish Apolemichthys trimaculatus is a very pretty, moderately sized angel. Bright yellow overall, it is accented with an alluring purple mouth and a prominent black spot on its forehead and can reach up to 9.8″ (25 cm). It is also commonly called the Three-spot Angelfish because of the spot on the forehead, one above the eye, and a faded spot behind each gill cover.

The Apolemichthys genus contains only 9 species of angelfish with the Flagfin being one of the most commonly imported. This group contains some of the hardiest of the angelfishes, but unfortunately the handsome Threespot Angelfish is not one of them. are not easy angelfish to maintain in the aquarium long term due to their dietary requirements.

These angelfish are difficult to keep and so are suggested for more experienced aquarists. They are extremely timid and easily stressed. Consequently they don’t handle shipping very well and are easily intimidated, then they only want to eat foods they recognize. Their natural diet consists of sponges, tunicates, benthic algae and weeds. Adults and very small juveniles are especially difficult to ship and generally refuse to eat. Its best to obtain young specimens between 2- 4 inches (5 – 10 cm) in length as they the easiest to acclimate.

The ideal tank for them is a mature reef type aquarium that is at least 100 gallons (378 liters). They need rockwork creating lots of caves for refuge, a lot of open swimming area, and tank mates that are peaceful. They do tend to be picky feeders, especially as adults. So having live rock and a good algae growth in an established tank can help them to acclimate. You can also help them acclimate initially by providing sponges until they learn to eat the new foods that you are providing. Once established however, they will accept a variety of aquarium foods. Be sure their diet includes plenty of plant matter. Offer prepared foods that contain spirulina as well as sponge material and meaty foods.

This angelfish can be kept in a community aquarium and even mixed with other angelfish if the aquarium is large enough. It is a semi-aggressive but can be easily intimidated when first introduced to the tank. The best tank mates are those that are not overly excitable feeders or overly aggressive. This angelfish is considered one of the safer choices for a reef aquarium as they tend not to pick on sessile invertebrates. But as with many of the large angelfish, an older adult can start to reek havoc on the reef, so be cautious. In a reef setting they will eventually eat most of the sponge and any other corals, so are not a great candidate for a mini reef.

For more Information on keeping saltwater fish see:
Marine Aquarium Basics: Guide to a Healthy Saltwater Aquarium

Threespot Angelfish or Flagfin Angelfish (Apolemichthys trimaculatus)

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Threespot Angelfish feeding in an aquarium.

The Threespot or Flagfin Angelfish, Apolemichthys trimaculatus, does not commonly do well in captivity, unless the aquarist is willing to spend time housing it properly and getting it to feed. Lots of mature live rock is a necessity with algae, tunicates and sponges growing on it. This will enable them to feed off these natural foods on the rock until they can be coaxed into eating prepared foods with sponge material. Do not keep with boisterous feediers or any aggressive fish since it will hide, not feed and starve to death. They are bullied by dwarf angelfish. Provide a tank that is at least 100 gallons and plenty of hiding places.

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Pomacanthidae
  • Genus: Apolemichthys
  • Species: trimaculatus
Three-spot Angelfish – Quick Aquarium Care
  • Aquarist Experience Level: Intermediate
  • Aquarium Hardiness: Difficult
  • Minimum Tank Size: 100 gal (379 L)
  • Size of fish – inches: 9.8 inches (24.89 cm)
  • Temperament: Peaceful
  • Temperature: 73.0 to 84.0° F (22.8 to 28.9&deg C)
  • Range ph: 8.0-8.4
  • Diet Type: Omnivore
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Habitat: Distribution / Background

The Flagfin Angelfish Apolemichthys trimaculatus was described by Cuvier in 1831. This angelfish is a member of the Pomacanthidae family of the Apolemichthys genus, which currently has only 9 described species. They are found in the Indo-West Pacific covering from the south eastern coast of Africa all the way to Samoa, then from the southern part of Japan all the way south to Australia’s northern coast and surrounding northern islands. It is on the IUCN Red List as Least Concerned (LC) with a stable population.

Other common names it is know by include Three-spot Angelfish, Threespot Angelfish, Three spot Angel, and Three Spot Angelfish. These are descriptive names for its 3 spots on the body including one on the forehead, one above the eye, and a faded spot behind each gill cover. Juveniles also have a black spot near the top back of the body and are very similar in appearance to young Goldflake AngelfishApolemichthys xanthopunctatus.

The typical habitat of these angelfish consists of seaward reefs and lagoons near corals. They feed on sponges, tunicates, benthic algae and weeds, all of which were found in the stomachs of both adults and juveniles. They inhabit depths from 9 to 196 feet (3 – 60 m), with juveniles staying below 80 feet (25 m) on the deeper fore-reef slopes. Adults can be found alone and in pairs, or even form small, loose groups in areas where the species is numerous. Juveniles are usually solitary, being very secretive and hiding within rock work.

This species is closely related to, and hybridizes with the Indian Yellowtail AngelfishApolemichthys xanthurus in the wild. The offspring were originally thought to be a distinct species. They were called the Armitage Angelfish and initially described as Apolemichthys armitagei, though are now known to be a hybrid.

Author Scott W. Michael, in his book , describes the Armitage Angelfish hybrid as variable, but typically with a darker dusky upper back and yellow spots on their scales which gradually brightened to a more solid yellow toward the belly area. The head is darker and a black patch is found on the top edge of the tail fin. This hybrid is reported as hardy, accepting flake food which is typical of the Indian Yellowtail Angelfish A. xanthurus parent.

  • Scientific Name: Apolemichthys trimaculatus
  • Social Grouping: Pairs – Solitary as juveniles. Adults are found solitary, and as population densities increase, they can be found in pairs or small, loose groups.
  • IUCN Red List: LC – Least Concern – Stable population.


The Flagfin or Three-spot Angelfish has an elongated, oval, flat body. It is a bright yellow over all, though it will darken when intimidated, and the lips are blue. There are black spots on the forehead above each eye, and a faded spot on each of the gill covers. The adult has a yellow to white anal fins that are black on the bottom half. These fish will grow up to 10″ (26 cm) in length and can have a lifespan of 10 years or more. Marine angelfish are known to live from 10 to 20 years in captivity.

Juvenile Flagfin Angelfish, Apolemichthys trimaculatus Flagfin Angelfish, JuvenilePhoto © Animal-World:
Courtesy Hiroyuki Tanaka

Juveniles are a little less elongated. They have a black line on the forehead, a black line through each eye, and a black dot or false eye to deter predators. on the upper rear of the body. The juvenile lacks the blue lips, but generally has the half black anal fin.

  • Size of fish – inches: 9.8 inches (24.89 cm) – Purchase sizes between 2 to 4†(5 – 10 cm) for best success.
  • Lifespan: 10 years – As with most marine angelfish, the Threespot can live over 10 years with proper care, yet this is rarely attainable in captivity.

Fish Keeping Difficulty

The Flagfin Angelfish is difficult to keep, so are best kept by experienced aquarists. They are extremely timid and easily stressed. Smaller individuals and adults do not ship well and refuse to feed most of the time. Then once acclimated, keeping them long term is a challenge due to their dietary requirements. Obtain juveniles between 2 to 4″ (5 – 10 cm) in length for best success.

Providing live rock with lots of algae crops, along with live sponges and tunicates can help to acclimate it to prepared foods. A mature tank of at least 100 gallons (378 liters) is needed, and no dwarf angelfish or other angelfish tank mates that will pester this angelfish, or intimidate it into not eating as it is acclimating, is a must. Starting out your fish in a reef like environment may be what is necessary to keep them alive longer, though eventually it will eat most of your corals. After the corals are gone, enough lighting is still needed to grow algae for them to graze on. By then, hopefully they have switched to eating some prepared foods.

Author Roger C. Steene, in his book, Butterfly and Angelfishes of the World, suggests “the tank walls should be covered with algae and the hobbyist should offer mysis, artemia (frozen), flake food, freeze dried red mosquito larvae, and enchytrae.”

  • Aquarium Hardiness: Difficult – Dietary needs and tank size are cost prohibitive for most aquarists.
  • Aquarist Experience Level: Intermediate – Intermediate to advanced.

Foods and Feeding

The Flagfin Angelfish is an omnivore. In the wild they primarily eat sponges and tunicates along with algae, so any high quality sponge based foods are necessary. They do best with live rock that has plenty of algae growth. Use live mysis shrimp or live brine shrimp to initiate a feeding response. Provide sponge based material to supplement the algae they are eating on the live rock. Also mashing food into areas where a sponge once was, but is already eaten up, may help them adjust to the taste of prepared foods. Once acclimated, enriched meaty foods can be offered, but should not be the bulk of their diet.

It is best to feed small amounts several times per day. It’s also important that you feed angelfish a variety of good foods; all kinds of live, frozen, and prepared formula foods. Feed them prepared frozen foods with spirulina, foods with sponge material and algae sheets as well. Chopped fish and shrimp, along with enriched mysis and brine shrimp should also should be provided. A good formula that can be made at home consists of mussels, shrimp, squid, and spinach. There are also several good commercial foods available including Formula II and Angel Formula.

  • Diet Type: Omnivore – Needs algae, sponge and tunicates as main foods with little meaty foods.
  • Flake Food: Yes – With sponge material added.
  • Tablet / Pellet: Yes – With sponge material added.
  • Live foods (fishes, shrimps, worms): Some of Diet – Use to initiate a feeding response in new arrivals. Feed live mysis and algae based foods first.
  • Vegetable Food: Half of Diet
  • Meaty Food: Some of Diet – Offer highly enriched meaty foods as a treat, but not regularly.
  • Feeding Frequency: Several feedings per day – Once sponge and tunicates in tank have been consumed feed prepared foods with these items in the ingredients.

Aquarium Care

Excellent water parameters are key in helping to keep this angelfish healthy. In the minimum sized tank of 100 gallons (378 liters), perform 20% water changes bi-Weekly, more if overstocked. A water change of 30% should be performed with very large tanks over 100 gallons, unless the tank is sparsely populated and water parameters are showing very good quality.

As with all angelfish, keeping the pH at 8.0 to 8.4 is ideal. The pH should never drop below 8.0. Controlling pH levels is best resolved by water changes rather than chemicals. Using testing equipment is suggested to tell you when to do a water change.

  • Water Changes: Bi-weekly – Water changes of 20% bi-weekly for the minimum sized 100 gallon tank (378 liters).

Aquarium Setup

They can do well in a typical reef setting with live rock and places to hide, but also make sure there is open area for the Flagfin Angelfish to swim. A tank that is at least 100 gallons (378 liters) is needed, with lots of algae growing on the rocks, and aged at least 6 months. Provide Water parameters of: 73-84? F, pH 8.0-8.4, sg 1.023-1.025. Form several hiding places within the rock work, to help your angelfish feel secure.

Not eating and stress are what cause failure with the Three-spot Angelfish. But if provided food, the stress will subside as your Threespot Angelfish recognizes you as a source of food as well. When first acquiring your angelfish, stocking the tank with sponges and tunicates, which they eat in the wild, will help them to slowly acclimate. Observe the new fish from a distance and allow feeding to begin. After a few days of feeding off your well stocked tank, add some prepared foods. Put sponge material near some of the sponges you see your fish eating to acclimate him/her to the taste. With patience and peaceful tank mates, your angelfish will feel brave enough to come out and feed. In a tank over 150 gallons, a mated male female pair may be kept.

  • Minimum Tank Size: 100 gal (379 L) – In a tank over 150 gallons, a mated male female pair may be kept.
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Plus Hiding Places
  • Substrate Type: Any
  • Lighting Needs: Any
  • Temperature: 73.0 to 84.0° F (22.8 to 28.9&deg C)
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.0-8.4
  • Brackish: No
  • Water Movement: Any
  • Water Region: Bottom

Social Behaviors

The Threespot Angelfish is peaceful and works great in a large peaceful community tank. They only become aggressive toward their own kind and other fish of similar color/shape. Do not house with dwarf angelfish, since dwarf angelfish will bully them into not eating and eventually starvation. Clownfish and anthias, though considered semi-aggressive should be okay, just watch for bullying. These angelfish will exhibit a darker coloration when they feel intimidated.

They are not considered reef safe, paradoxically, this is what they need to survive in captivity. Though juveniles may be okay in a reef environment for a short time, adults will eventually eat most corals. Housing this angelfish in fish only aquariums is generally done. Yet they do best if started in a reef setting with live algae growing on rock for them to eat. Appropriate lighting for algae growth is needed at least until they will eat all prepared foods. Once fully acclimated, some of the more peaceful angelfish can be added as tank mates in tanks over 150 gallons (568 liters).

If you want to keep them with other angelfish, the tank should be at least 150 gallons with the following guidelines:

  • The tank should be mature, over 6 months.
  • There should be many hiding places, several for each angelfish. Having lots of places to hide and plenty of room to swim will help the more docile angelfish avoid the ?higher ups? in the tank.
  • When introducing the first angelfish, they should be the most peaceful of the different genus? such as the Flagfin Angelfish.
  • Always introduce the more aggressive fish last.
  • You may place juveniles of two different species, and two different sizes. Make sure you do not put them with other juveniles that are of the same coloration.
  • Before adding a new angelfish to a tank with an existing angelfish, feed the tank first.
  • If the new fish is harassed, rearrange the rock work and turn the lights off for the rest of the day.
  • Remove any angelfish that are constantly fighting and which is resulting in physical injury to each other.

These guidelines can also apply in general when adding other types of fish.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Sometimes – Only mated male/female pair. Will spar with other fish of similar size, shape, and color.
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor – Dwarf Angelfish should not be housed with the Threespot Angelfish. A pygmy angel will bully and intimidate the Three-spot, eventually causing it to not eat and starve.
    • Threat
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Threat
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat
    • Threat
    • Anemones: Threat
    • Mushroom Anemones – Corallimorphs: Threat
    • LPS corals: Threat
    • SPS corals: Threat
    • Gorgonians, Sea Fans: Threat
    • Leather Corals: Threat
    • Soft Corals (xenias, tree corals): Threat
    • Star Polyps, Organ Pipe Coral: Threat
    • Zoanthids – Button Polyps, Sea Mats: Threat
    • Sponges, Tunicates: Threat
    • Shrimps, Crabs, Snails: Safe
    • Starfish: Monitor – May nip at appendages.
    • Feather Dusters, Bristle Worms, Flatworms: Threat
    • Clams, Scallops, Oysters: Threat
    • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

Flagfin Angelfish (Three-spot Angelfish) do not display sexual dimorphism. The sex is unknown, though males may be larger.

Breeding / Reproduction

The Flagfin Angelfish has reportedly spawned in a larger public aquarium. Successful breeding most likely 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.

Three-spot Angelfish or Flagfin Angelfish Three-spot Angelfish

Angelfish generally are broadcast spawners, releasing eggs and sperm simultaneously at dusk. They dance then rise into the water column and release their eggs and sperm near the top of the water. Spawning starts before sunset with females extending all her fins as she swims next to the male. The male will go under the female and nuzzle her belly, then darts down about 2.3†to 3.9†(6 to 10 cm). The female then turns to her side and both release a white cloud of gametes containing sperm and eggs. Both males and females may mate with several others on the same evening.

  • Ease of Breeding: Unknown

Fish Diseases

Flagfin 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. Providing an angelfish with clean water, a proper decor with places to hide, and regular feeding is the best way to prevent illness. Calm angelfish are healthy fish. If not stressed, they will have a stronger immune system to prevent infections. To avoid a condition called nutritional blindness in angelfish, which can occur around 6 to 8 months after taken into captivity, feed green leafy food that have Vitamin A, as well as making sure there is plenty of natural occurring algae in the tank.

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.

A viral infection, Lymphocystis, looks like small cauliflower-shaped nodules on the fins and mouth. These nodules are not harmful and come and go. The only time action may be needed is if they were on the mouth area of the fish, preventing it from eating for a prolonged period of time. It’s best to do water changes to help the fish’s natural immune system kick in.

Monogenetic flukes are the most common parasitic infections angelfish are prone to contracting. 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.

Fish problems can be broken into one of (or a combination of) these types: parasites, bacterial disease, fungal disease, or physical ailments caused from deficiencies in diet as well as wounds and injuries. For more information on diseases that saltwater angelfish are susceptible to, see Aquarium Fish Diseases and Treatments.


Flagfin Angelfish, orThree-spot Angelfish, are generally available from time to time, and are moderately to higher priced angelfish.