Royal Angelfish (Pygoplites Diacanthus / Regal Angelfish)

royal angelfish

Last updated on July 3rd, 2022 at 12:42 pm

The royal angelfish (Pygoplites diacanthus / or sometimes referred to as the regal angelfish) lives in the Western Pacific, including the Coral Sea and Indonesia, Queensland, Australia, and New Caledonia in lagoons and rocky areas with rich growths of soft corals; also in shallow water on reefs. This species feeds on sponges, tunicates, bryozoans, hydroids, and other colonial animals; its diet changes with age.

Royal angelfish are beautiful fish with royal-blue bodies and bright orange fins, earning them the nickname royal blue angelfish. The bright colors of these fish will really stand out in your aquarium, and they’re not too difficult to care for if you follow these tips on how to keep a royal angelfish alive in an aquarium!

Pygoplites diacanthus is one of two species in the Pygoplites genus, along with Pygoplites salangonius. While both species have been classified by some researchers as belonging to the Centropyge genus, the classification of these fish continues to be disputed by other experts, who suggest that they should be placed in their own genus instead.

Origin and description

royal angelfish

The royal angelfish is a species of marine fish in the family Pomacanthidae. The fish is also called Regal Angelfish, which is more commonly used in stores to market varieties of Pygoplites diacanthus. Its common names include royal butterfly-fish, royal pomacanthid, and regal angelfish. It is found in reefs off Hawaii and Fiji and often inhabits caves, under ledges, and overhangs within its range.

Its habitat ranges from Nihoa to Australia. Despite being called a royal angelfish or regal angelfish, it has no connections with royalty or nobility: it just looks that way! This is a popular aquarium fish that can reach 36 cm (15 in). It gets its royal blue color from certain types of algae that live on its skin; if the algae are knocked off, the fish rapidly turns gray and loses much of its appeal for humans.

Species profile

royal angelfish

The regal angelfish, Pygoplites diacanthus, is a fish from the family Pomacanthidae. They can be found in tropical climates in Australia, and some Pacific islands. They are popular aquarium fish for their distinctive coloration and lifespan. While they are sold as juveniles, they do not reach maturity until they are between six and eight years old. If properly taken care of, they have been known to live up to thirty years!

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A common misconception about royal angelfish is that their scientific name (diacanthus) means two spines; it actually means thorny spine. This refers to one of its unique characteristics: a very prominent dorsal spine that grows longer as it ages.

Regal angelfish scientific name

The scientific name of the regal angelfish is Pygoplites diacanthus


The regal angelfish inhabit warm waters and are not found in cooler waters. They live in coral reefs, rocky outcroppings, and lagoons. The largest of their family, Pygoplites angelfish are only found around Madagascar. These fish feed on algae, sponges, tunicates, mollusks, bristle worms, and hydroids. They also will consume coral polyps from damaged or dead corals to supplement their diet with calcium for egg production.

Regal angelfish size

Royal angelfish reach an average length of 9 inches, but they can reach up to 15 inches (36 cm).

Regal angelfish tank size

The royal angelfish require a minimum of 100 gallons (375 L) with plenty of live rock for hiding and swimming space.

Tank set up

Royal angelfish are more delicate than other species of fish and are kept in tanks with strong filtration. The pH level should be between 8.1 and 8.4, and levels of nitrate should be between 5 and 20 ppm. A large tank is recommended for these fish because they are rather territorial, so it is best to keep them singly or in pairs to avoid conflict with others of their own kind.

Tanks also need plenty of live rock with areas that have caves and crevices for hiding. You can substitute live rock with some type of manufactured artificial reef if you wish, but make sure it has places where the royal angelfish can retreat.

Regal angelfish tank mates

This fish gets along well with other angelfish. It can also be kept with most brackish water fish that aren’t too large to eat them. Tank mates can include snails, shrimp, plecos, and loaches. They do well in pairs or small groups.

Their most common neighbors are shrimp and cardinalfish.

Royal angelfish breeding

royal angelfish

The Royal angelfish is not a difficult fish to breed, as long as you are willing to devote time and energy. The first and most important aspect of breeding them is getting a pair that are compatible. If a male and female are forced together that aren’t interested in each other, they can become very stressed.

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I recommend checking out our guide to breeding angelfish or asking a local club for help if you can’t find any resources locally. If a pair does start to form some bonds, their tank should be at least 200 gallons with lots of places for spawning sites. They need good filtration but don’t need intense lighting. A sandy substrate and a lot of rockwork are best. You will also want to provide plenty of food in order to keep them healthy during their incubation period, which can last up to five months!

To monitor whether your eggs have been fertilized, your female should lay her eggs on a live rock where you will be able to see whether she has been impregnated by looking for developing larvae. She will typically spawn every two days until she has laid 50 to 200 eggs. When the time to hatch comes, it may seem like nothing is happening since angel fry can remain motionless for several days after hatching.

During this period, feed them baby brine shrimp twice a day while continuing with daily water changes and check often on their progress. Once they hatch and move away from eggshells into open water, then begin feeding nauplii every day or every other day based on how many appear hungry.

Are Regal angelfish aggressive or peaceful?

The Royal Angelfish is a non-aggressive species, and won’t nip at your fingers if you hand feed them. They are fairly territorial and will defend their cave or an area of rocks, but shouldn’t be aggressive towards other species. Be careful to not overcrowd their tank as they don’t like to compete for resources.

The royal angelfish are generally peaceful fish and get along well with others of their own kind and other similar size fish that are not fin nippers.

Regal angelfish care

royal angelfish

This angelfish is a hardy fish that can be kept in an aquarium. Since it grows to about 15 inches, larger aquariums are preferred. The water should be slightly alkaline and moderately hard, with a pH of 8.1 of 8.4 and a specific gravity of 1.019 – 1.025 at 77 degrees F. Ideally, keep your royal angelfish in a marine environment with a temperature between 75 to 80°F and salinity around 30 ppt.

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However, it can tolerate warmer waters as well as cooler ones, so long as their care requirements are met. It should be fed a variety of flake food and other carnivorous foods such as bloodworms and brine shrimp once or twice a day. Most types of invertebrates also make good food for these angels. If possible, feed live brine shrimp occasionally to give them some variety in their diet.

What do royal angelfish eat?

The royal angelfish is a carnivore that feeds on small crustaceans, worms, and sea urchins.  They also have been known to eat smaller fish of their own species in captivity; make sure to provide plenty of live rock with hiding places for your fish so he won’t snack on his tank mates. Royal angelfish are very patient hunters, they’ll often wait motionless at an opening in their rockwork until they can snatch up something tasty swimming by!

Water parameters

royal angelfish

Royal angelfish are native to a tropical climate with water temperatures ranging from 21.7 to 30.2°C (71.1 to 86.4°F). However, they can tolerate a more temperate range of 23 to 27°C (73.4 to 80.6°F), which they tend to prefer because it is closer to their ideal temperature of 25°C (77°F). If temperatures exceed 30.2°C (86.4°F), water quality deteriorates quickly and disease may occur as a result of stress on your fish’s immune system and increase the risk for bacterial infections like fin rot or tail rot and fungal infections such as whiptail fungus.

Royal angelfish do best in moderately hard, alkaline water that is higher in nitrates and lower in phosphates. They will survive, however, in hard, neutral water if they are provided with a proper diet and live foods. They are very sensitive to ammonia and nitrite spikes so you must use caution when performing any type of tank maintenance or cleaning. It’s also critical that these fish be kept in an aquarium set up for reef tanks.

This means no aquarium rocks, as these angelfish love to dig and burrow into things. And finally, keep your lighting on the brighter side as these fish need bright lighting levels to flourish.

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Regal angelfish lifespan

They can live up to 15 to 20 years if cared for properly in captivity. In their natural habitat, they have an average lifespan of 8 years.

Parasites and diseases

Some parasites of reef fish can harm your angelfish. These include marine ich and anchor worms, both of which attack externally. Marine ich is a protozoan parasite, while anchor worms are flatworms or nematodes that latch onto your fish’s body to suck its blood and lymph, often killing it in a matter of days.

Symptoms include red spots on fins and skin loss, typically around infected areas. Treatment includes salt baths and praziquantel injections, though it won’t save your fish if severe damage has already been done. You may also want to treat any other tankmates with any parasitic infections before reintroducing them into an angelfish tank; these infections can spread quickly between tankmates.


Juvenile Royal angelfish are preyed upon by a variety of other reef fish, such as barracuda, smaller groupers, and lionfish. They can also be threatened by over-collection from hobbyists or habitat destruction through development.

Do royal angelfish make good pets?

Royal angelfish are a fantastic addition to any saltwater aquarium, and they’re not difficult to care for if you set up your tank properly and maintain it. Because of their coloration, they can make a stunning centerpiece or focal point in your aquarium.  They also have been known to live for more than 10 years when cared for properly, so don’t be surprised if one outlives you!

Their biggest drawback is that they are difficult to come by, as very few aquarists have had success breeding them in captivity. For these reasons, royal angelfish should only be kept by hobbyists with years of experience keeping saltwater fish, but once you find one at a local fish store or online retailer, get it quickly!