Pomacanthus semicirculatus – Koran Angelfish

Pomacanthus semicirculatus – Koran Angelfish grow to about 40 centimeters, they need a large aquarium of at least 700 liters if kept alone. Much larger in a community tank.

Pomacanthus semicirculatus – Koran Angelfish

Koran Angelfish or Pomacanthus semicirculatus belong to the family Pomacanthidae. This species is endemic to the Indo-Pacific and the Rea Sea as far east as Samoa. Their geographical range stretches from Japan down the entire east coast of Africa to Western Australia and New South Wales. These are marine reef fish, occupying depths from 3-100 feet.


One of the common traits among large saltwater angelfish is the dramatic transitional color change between the juvenile and adult phases of their lives. It is simply amazing watching a juvenile’s gradual metamorphosis into its adult color palette. Koran angelfish fish undergo three distinctive stages on the sojourn to adulthood.

First stage

The Greek word semicirculatus refers to the initial phase of their life. Baby Korans have black bodies with blue and white striping that expands concentrically forward from the base of their tails. This patterning very much resembles ½ of the ripples on a still pond when a pebble is suddenly dropped into it. A baby Koran could easily be mistaken for a juvenile Emperor Angelfish – Pomacanthus imperator or a Pomacanthus annularis. Closer examination reveals that Koran’s have wider stripes and fewer of them.

Second stage

When these fish reach about 3 inches in length the semicircular markings slowly straighten into sweeping lines. At roughly five inches in length the fish begins to exhibit patterning between the blue lines on the tail fin that resembles Arabic script, hence the name Koran angelfish. They will exhibit a combination of juvenile and adult coloration. This marks the conclusion of stage two. At approximately two years of age and between 6-7 inches in length this species morphs into its adult color palette

Adult coloration

Adults are typically a yellowish green in color with varying amounts of blue or browns spotting on their bodies and caudal fin. Their heads may be blue or their primary body coloring. Gills and fins are outlined in blue. This species is marketed by the aquarium industry under the following names; Koran Angel, Blue Koran Angel, Half-circle Angel, Half-circled Angel and Semicircle Angel.

The Aquarium

These fish will grow to a maximum adult length of 16 inches. Because of their size they will require a large aquarium. A minimum tank size of 135 gallons is recommended. A well populated multi-species tank should be considerably larger. This fish has a semi-aggressive temperament. It may bully smaller fish. It will for the most part ignore other larger species. It will, however, display major territorial behavior toward conspecifics and other angels. It is advisable to only keep a single large angle fish of any species in an aquarium.

Many species of large angles carry an expert care level. Korans are rated moderate. Large angels in general have exceptionally high mortality rates in captivity. Here are some handy tips to help you insure your angle’s survival. Do not choose a baby or an adult specimen. Babies have not yet developed a strong enough constitution to endure the transition into a life of captivity. They are far more susceptible to improper handling techniques during capture and transport.

Feeding in captivity

Adults have spent their entire lives in the wild. It may well prove extremely problematic getting them to feed and then further modifying their behavior patterns to accept non-living food offerings. Juveniles are generally hardy enough to endure the acclimation process between their native habitat and life in an aquarium. Additionally, since they have not yet grown to their full size they are much more likely to fit into a pre-established population. A 4-6 inch juvenile is ideal for a community tank.

Buying Pomacanthus semicirculatus

Always make sure an angelfish does not show signs of labored breathing before making a purchase. Angelfish are susceptible to gill-burn from improper shipping and poor water conditions. At normal activity levels the fish’s gill should open approximately once per second. Always choose a specimen that has a full body and face. Hollowed out features are a sure sign of malnutrition. Ask to see the fish feed before making a purchase. A fish that is feeding for the pet store is more likely to feed for you. Choose an active fish with full fins. Sluggish fish and ones with tattered fins may be in the early stages of disease. Look for clear and shiny eyes. Also make sure the fish’s body color is uniform. You do not want a specimen with white blotches, blemishes or pitting.


Last but definitely not least, put a deposit on the fish you intend to purchase or have the retailer quarantine it for at least three weeks before taking it home. If you own a quarantines tank, an additional isolation period of two weeks before introducing your angelfish to the general population is advisable. Angelfish are long lived species. A healthy Koran may live 15-20 years.


Korans are omnivorous. In nature their diet consists of a mixture of sponges, corals, algae, worms, mollusks and crustaceans. Needless to say this species will not make a suitable candidate for a marine reef aquarium. Begin training them to accepting non-living food offerings by mixing larger and larger amounts of flake, pellets or frozen preparations with live brine shrimp. Once they have been successfully acclimated, the protein part of their dietary needs can be supplemented with chopped crustaceans and mollusks. They should also be fed a variety of algae and plant matter. Chopped spinach, zucchini, yellow squash, and broccoli are suitable veggies. Try experimenting to see which ones they find the most appealing.


Algae are an essential part of an angelfish’s diet. An abundance of well established live rock is mandatory for properly maintaining theses species. Dried algae sheets will help insure optimum nutritional intake. Products such as Ulva (sea lettuce), Nori, Kombu, and Caulerpa can be purchases at most Asian food centers.



Exotic-Aquariums (no longer online)

Copyright foto’s

Klaus Stiefel
Russell Gilbert
Elias Levy
Rickard Zerpe – CC BY 2.0

Last Updated on 6 October 2021 by John

Additional information






Holacanthus alternans, Holacanthus lepidolepis, Holacanthus reginae, Holacanthus semicirculatus, Pomacanthops semicirculatus

Common names

Koran Angelfish


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