They call this a Keyhole Angelfish because of the white spot that looks just like a “keyhole”!

The blue-black colored Keyhole Angelfish Centropyge tibicen is the largest species of dwarf angelfish recorded to date. Though these dwarf Angelfish are often less than 4.7″ (12 cm), they can reach an impressive 7.5†(19 cm). They are also called the Tibicen Angelfish and Melas Angelfish.

The overall coloration of the Keyhole Angelfish is a dark blue-black with a contrasting white “keyhole†patch on the sides. They have yellow pectoral and anal fins below, and a blue margin edging the tail fin. Though not as vibrantly colored as many of the other pygmy angels, this clever black/white contrast with the yellow and blue accents, makes it a striking attraction in the tank.

The Keyhole Angelfish is best in a “fish only with live rock” aquarium (FOWLR). In the wild they feed mostly on algae, but also some crustaceans. They need quite a bit of algae to graze on daily, along with several feedings a day. A decent sized tank, at least 55-60 gallons, with algae growing on live rock is recommended. A tank that is 100 gallons or more will be needed for a pair. Within the tank, offer plenty of hiding spaces and algae growth to forage on within the rocks.

These dwarf angels are semi-aggressive. Although initially secretive, once they become established they will bully fish that are similar in shape, size, or eating behavior. They will also be aggressive towards other Centropyge species as well as other fish added to the tank after it. Those with beloved reef tanks have to sit this dwarf out, since it will dine on most of your corals. It may leave mushrooms alone, but even that is not ruled out.

When buying a Keyhole Angelfish, look for one that is alert and actively looking for food. They should look well fed and like other dwarf angelfish, they should be quick to hide, yet curious enough to come right back out to size you up. Be cautious of dwarf angelfish from the Philippines. Poor capturing practices of some fishes, not allowing the fish to decompress as they are taken from the depths to shallower waters, can result in eventual death for up to about a month. Dwarf angelfish from Marshall and Christmas Islands, as well as any around Australia, seem to have consistently healthy stock.

Keyhole Angelfish are born female and can be paired according to size. The larger fish becomes male, so creating a pair may be possible by buying one large and one small Keyhole Angelfish. Within a few months they hopefully they will assume their roles as male and female, with some males showing a more bluish black cast.

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

Keyhole Angelfish (Centropyge tibicen)

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Keyhole Angelfish in the wild.

This Keyhole Angelfish looks like a female as the males have a blue cast to them. They are one of the more durable members of the Centropyge, or Dwarf Angelfish clan. As you can see by the behavior in the wild, they are constantly picking at algae and looking for food. Like all Centropyge, a tank of at least 50 gallons is needed to supply the natural foods that grow on the live rock.

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Pomacanthidae
  • Genus: Centropyge
  • Species: tibicen
Keyhole Angelfish – Quick Aquarium Care
  • Aquarist Experience Level: Intermediate
  • Aquarium Hardiness: Moderately hardy
  • Minimum Tank Size: 55 gal (208 L)
  • Size of fish – inches: 7.5 inches (19.05 cm)
  • Temperament: Semi-aggressive
  • Temperature: 72.0 to 82.0° F (22.2 to 27.8&deg C)
  • Range ph: 8.0-8.4
  • Diet Type: Omnivore
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Habitat: Distribution / Background

The Keyhole Angelfish Centropyge tibicen was described by Cuvier in 1831. This pygmy angel is a member of the Pomacanthidae family, of the genus Centropyge, which currently has over 33 species. It is on the IUCN Red List as Least Concern (LC) as this dwarf angelfish has a large population and a very wide distribution. Although they are harvested for the pet industry there are no major threats currently identified.

The Keyhole Angelfish inhabit the Western Pacific Ocean and the Eastern Indian Ocean. They are found in areas of Christmas Island to Fiji then northward to the southern part of Japan; southward to the Scott Reef, the Eastern Indian Ocean, and Lord Howe Island. Other common names they are known by are Tibicen Angelfish and Melas Angelfish.

The Keyhole Angelfish are found alone or in harems of 3-7 individuals. They inhabit mixed coral and rubble areas of lagoons and seaward reefs, feeding primarily on algae and some and crustaceans. The depths they are found as adults is from 13 to 180 feet (4 to 55 m).

  • Scientific Name: Centropyge tibicen
  • Social Grouping: Varies – It is seen alone or in harems of three to seven individuals.
  • IUCN Red List: LC – Least Concern – Stable population.


The Keyhole Angelfish has the typical shape for a dwarf species, having a small elongated oval shaped body with rounded fins. This dwarf angel, though often less than 4.7″ (12 cm), can grow to a maximum length of 7.5″ (19 cm). The larger specimens are from the waters of the Lord Howe Island. Keyhole Angelfish reportedly can live up to 6 years in the wild though are generally longer lived in the aquarium, up to 10 years with good care.

This dwarf angelfish ranges in overall color from dark bluish black to black. It has a vertical white oval blotch on the upper back below the dorsal fin toward the front, giving it rise to its common name.The anal fin can be all black, or the part closest to the body being black with the bottom half being white or yellow, and having a blue or white thin line dividing the halves. There can also be a thin blue line at the outer edge of the dorsal and anal fin in some specimens. The pelvic fins have different intensity levels of yellow, which seems to coincide with the anal fin coloration. The pectoral fins are slightly transparent. As a juvenile the Keyhole Angelfish are black with a white bar which then shrinks to a ‘keyhole’ type blotch.

Interestingly, a golden specimen (xanthic) has been reported. This specimen was a light orange color on the front half of the body and pinkish white on the back half. The “keyhole” spot was a lighter white and there was a yellow border on the anal fin.

  • Size of fish – inches: 7.5 inches (19.05 cm) – They are often less than 4.7″ (12 cm). The larger specimens are from the waters of the Lord Howe Island.
  • Lifespan: 10 years – It’s reported that they can live up to 6 years in the wild and up to 10 years in captivity.

Fish Keeping Difficulty

The Keyhole Angelfish are moderately hardy and suggested for an intermediate marine aquarist. They can be easy to moderate to care for if you are careful to get a healthy individual who is alert, eating, and curious.

They need a mature tank that is minimum of 55 gallons (208 l) with plenty of algae growth. Provide rock work with multiple places to hide so they will feel secure enough to come out. Do not let pH drop below 8.0 and nitrates need to be very low. Any nitrites can be lethal.

  • Aquarium Hardiness: Moderately hardy – They can be easy to moderate to care for if you are careful to get a healthy individual who is alert, eating, and curious.
  • Aquarist Experience Level: Intermediate

Foods and Feeding

The Keyhole Angelfish is an omnivore. In the wild their diet mainly consists of algae along with some crustaceans. They need algae naturally growing in the tank to be healthy. Feeding them several times a day and offering a variety of good foods is important even with amply algae in the tank. These include prepared foods with marine algae, spirulina enriched foods, frozen mysid shrimp, brine shrimp, and meaty crustaceans such as shaved shrimp and clams. There are several good commercial foods available including Formula II and Angel Formula.

  • Diet Type: Omnivore – Feeds primarily on algae along with some crustaceans. Offer a diet with Spirulina algae and sponge material included.
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Most of Diet – They feed primarily on algae.
  • Meaty Food: Some of Diet – Though leaning more towards algae consumption, they will consume some proteins.
  • Feeding Frequency: Several feedings per day – Feedings depend on the size of the tank. Generally they should be fed 2 to 3 times a day, with less in a tank with a lot of natural algae sources. However, if it is a larger tank with more algae for them to forage from, then feed 1 to 2 times day.

Aquarium Care

The Keyhole Angelfish is moderately difficult to keep. Water quality and tank size are important. Keep in mind these angelfish are constant grazers and like tangs, lots of food in equals a lot of bio load, so water quality must be monitored. They need a pH of at least 8.0, and water changes that do not include scrubbing all the algae off of the rock. When performing your water changes, one time you can clean the left side of the tank by dismantling and vacuuming the rock and sand. During the next water change, clean the other side the same way.

Water changes of 30% a month, or 10 to15% every 2 weeks is optimal in keeping nitrates lower. If the tank is over 100 gallons, then do 20% every 3 weeks to a month. Keeping up with your water testing will tell you when your tank needs a water change, as these are just guidelines.

  • Water Changes: Bi-weekly – Water changes of 10 – 15% every 2 weeks, or 30% a month, is optimal in keeping nitrates lower and the water clean.

Aquarium Setup

They will do well in a typical reef setting with live rock and plenty of places to hide. The aquarium needs to be at least 6 months old or more to provide all the necessary algae to feed your angelfish. It is helpful ho have areas of rubble for the algae to grow on. This will aid in feeding them their needed vegetables and will also help make them feel secure. A minimum of 55 gallons is needed for one fish and 100 gallons or more for a mated pair. Even juveniles need an established tank that is at least 55 gallons.Provide water parameters of: 72-82° F, pH 8.0-8.4, sg 1.020-1.025. It is best to introduce the Keyhole Angelfish while young, and as the last addition to an established tank.

  • Minimum Tank Size: 55 gal (208 L) – A tank of at least 55 gallons with plenty of algae growth for a single specimen, and 100 gallons (378 l) or more for a pair.
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Plus Hiding Places – Hiding places are key to helping dwarf angelfish feel secure. A good amount of live rock to supply natural foods is also important.
  • Substrate Type: Any – All dwarf angelfish seem to appreciate a small area of the tank with rubble on which to forage off of for algae and other edibles.
  • Lighting Needs: Any – Lighting should be strong enough to support algae growth. If tank has low lighting, making sure direct sunlight hits the tank to support this natural food is suggested.
  • Temperature: 72.0 to 82.0° F (22.2 to 27.8&deg C)
  • Specific gravity: 1.023-1.025 SG – Angelfish in general do not do under 1.023 for long periods of time.
  • Range ph: 8.0-8.4 – Angelfish will deteriorate quickly under 8.0.
  • Brackish: No
  • Water Movement: Any – They like some areas of strong and weak movement. A weaker movement would be appreciated along the bottom for feeding.
  • Water Region: Bottom – They will also inhabit mid level areas of the tank.

Social Behaviors

The Keyhole Angelfish, like other members of this genus, is solitary and stays close to shelter. It is aggressive toward other fish in the same genus so should be kept alone in a 55 gallon tank. They can be kept as a male/female pair or small harem in a larger aquarium that is 100 gallons or more. Two males will fight to the death.

Once established, these pygmy angels are aggressive toward fish that are similar in shape, size, or eating behavior. If they are introduced last into a larger tank, they should get along with other tank mates that are of different size and shape. They do not get along with other dwarf angels. Reef tanks are out as they will nip corals, clams, and other sessile invertebrates.

  • Venomous: No
  • Temperament: Semi-aggressive
  • Compatible with:
    • Same species – conspecifics: Sometimes – Male/Female pairs or small harems can be kept in tanks over 100 gallons (378 l).
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Threat
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor – Will harass smaller fish like clowns and anthias if tank is only 55 gallons. Larger tanks, that are at least 75 gallons, with more hiding places will allow these semi-aggressive smaller fish to fair better.
    • Safe
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Aggressive toward fish that are similar in shape, size, or eating behavior.
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Monitor – Safe unless the tankmate is large enough to eat the Keyhole Angelfish.
    • Threat – Angel fish will out compete slow moving fish for food.
    • Anemones: Monitor – As long as a pugnacious clownfish is guarding the anemone, it should be okay.
    • Mushroom Anemones – Corallimorphs: Monitor – May eat waste exuding from mushrooms, which is not harmful, just keep an eye on the fish.
    • LPS corals: Threat – They may graze on the slime they exude preventing them from opening fully, which can cause eventual death of the coral.
    • SPS corals: Threat – They may graze on the slime they exude preventing them from opening fully, which can cause eventual death of the coral.
    • Gorgonians, Sea Fans: Monitor – They may graze on the slime they exude preventing them from opening fully, which can cause eventual death of the coral, but still monitor for individual preferences.
    • Leather Corals: Monitor – Safe with most from the Sinularia, Sarcophytom, Cladiella, and Paralemnalia genera, but still monitor for individual preferences.
    • Soft Corals (xenias, tree corals): Monitor – Safe with most from the Effatounaria genus, but still monitor for individual preferences.
    • Star Polyps, Organ Pipe Coral: Monitor – May nip at polyps if not well fed.
    • Zoanthids – Button Polyps, Sea Mats: Threat
    • Sponges, Tunicates: Threat
    • Shrimps, Crabs, Snails: Safe – Only the smallest decorative shrimp may be at risk. Large cleaner shrimp should be left alone.
    • Starfish: Monitor – May pick at appendages if not well fed.
    • Feather Dusters, Bristle Worms, Flatworms: Threat
    • Clams, Scallops, Oysters: Threat – They may graze on the slime they exude preventing them from opening fully, which can cause eventual death.
    • Copepods, Amphipods, Mini Brittle Stars: Safe – Will not decimate populations as it is not a obligate eater of these foods.

Sex: Sexual differences

Keyhole Angelfish, Centropyge tibicen Female – Keyhole Angelfish

Female Keyhole Angelfish are usually black overall, while the males tend to be dark blue. All Centropyge are born as female, as they grow, the larger and more dominant fish will become male and if the male dies, the angelfish next in line in the hierarchy will turn to male. Putting a larger and smaller fish together is the best way to get a pair, possibly in about 2 -3 months time.

Breeding / Reproduction

As of yet the Keyhole Angelfish have not been bred in captivity. In the wild, they 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.

It has been observed that all Centropyge dwarf angelfish have a similar spawning routine. Centropyge spawning typically consists of the male and female circling each other upon meeting, followed by the male making grunting noises. The male will then swim upwards off the bottom, and hover, tilting his body toward her at a 45 to 90 degree angle.

If she is ready to spawn, the female will join the male and both will soar together. When the soaring behavior is complete, this varies between dwarf angelfish species, the male will nuzzle her belly for up to 18 seconds, followed by the male flickering his pectoral fins and opening and closing his mouth. Suddenly, they are belly to belly, releasing gametes, producing fertilized eggs. These eggs are on their own and will not be protected by either parent. The pair will then rush back to the sea bottom with the male of this species making a rattling sound!

  • Ease of Breeding: Difficult

Fish Diseases

Providing a dwarf angelfish with plenty of places to hide and clean water is the best way to prevent illness. Calm fish are healthy fish. If not stressed, they will have a stronger immune system to prevent infections. Like other saltwater angelfish, dwarf angelfish can suffer any disease that captive saltwater environments have to offer. Fish problems can be broken into one of (or a combination of) these types: parasites, bacterial and fungal disease, or physical ailments (wounds and injuries). To learn all about fish problems and find specific answers, see Aquarium Fish Diseases and Treatments.

The best and first defense to prevent diseases is a quarantine period before introducing a new fish. Quarantine tanks should be bare with a PVC tube where the fish can hide. Do regular water changes every day or so. Secondly, fresh water dips can also help to kill anything that is on their body that may spread. PH and temperature must be the same (just use baking soda to bring up the PH if you have soft water but use a test). Start with 5 minutes and up to 15 minutes if they are not showing any signs of distress. This is really only needed if you see anything on their body or if the back fin is starting to fray.

Dwarf angelfish diseases and treatments:

  1. Parasitic and Protozoan diseases
    Dwarf angelfish are prone to parasites like White Spot Disease Cryptocaryon irritans, also known as Marine Ich, Saltwater Ich, or Crypt. Another common disease is Marine Velvet or Velvet Disease Oodinium ocellatum, (syn: Amyloodinium ocellatum or Branchiophilus maris), which is a parasitic skin flagellate. These are two of the most common diseases.
    – Symptoms of White Spot Disease are constant scratching and flashing, culminating with numerous white dots all over the body and fins. 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.
    – 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.
    • Treatment of parasites
      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.

      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.

      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.
  2. Bacterial Diseases
    As with all dwarf angels, they are also vulnerable to bacterial and fungal diseases. Bacterial infections are often a secondary infection resulting from damage caused by a parasitic or protozoan disease. One of concern is the Vibrio bacteria, which starts as an internal infection, turns into Dropsy, Popeye, Bleeding or Red Streaks on the skin. It is a very fast acting bacteria that will kill your angelfish in days. One way it typically starts is with an innocently frayed back fin. This disease will quickly spread and kill a fish within 2 days.
    • Treatment of bacterial diseases
      Fresh water dips are an important step to kill anything that is on their body that may spread. PH and temperature must be the same (just use baking soda to bring up the PH if you have soft water but use a test). Start with 5 minutes and up to 15 minutes if they are not showing any signs of distress. This is really only needed if you see anything on their body or if the back fin is starting to fray. Only treat in 1/2 doses any medications containing cleated copper as all angelfish are sensitive to this element in it’s free form.

      For dropsy, popeye, fin/tail rot and septicemia, which are at time secondary infections, another product you can use along with Seachems Metronidazole or alone is Seachems Kanaplex. You still need to use Focus to bond the Kanaplex to the food. Kanaplex, when used with Metronidazole in the same food, would be 2 scoops of Focus, 1 scoop of Kanaplex and 1 scoop of Metronidazole, yet this combination should only be fed once a day for 7 days, since Kanaplex should only be used for 7 days maximum. If you need to continue past 7 days, use only Metronidazole in a separate mixture for further treatment. This product can also be added to the water (without focus) if the fish is not eating.
  3. Physical Ailments
    Physical Ailments are often the result of the environment, either water conditions or incompatible tankmates. Poor quality water conditions can lead to fish gasping, not eating, jumping out of the tank, and more. Dwarf angelfish when very stressed or being picked on will hover in the upper corner of the tank and should be removed if the fish bullying your angelfish is not. Tank mate problems can result in nipped fins and bite wounds..
    • Treatment for physical ailments
      Look for and remove bully fish.
      Products on the market to help include stress relievers like Melafix, Wound Treat, and Bio Bandage.


The Keyhole Angelfish is usually available online and in stores, and is moderately priced.


 Keyhole angelfish (Centropyge tibicen) (Image Credit: Rickard Zerpe, Wikimedia Commons CC BY-SA 2.0 Generic)