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What is it that makes a captive marine species your favorite? Hardiness and beauty surely; intelligence, even grace is desirable. Practically speaking, low-cost and easy-availability are important issues. With this large Indo-Pacific angel we have all these traits, in spades. Truly a "best" in its family, P. semicirculatus is amongst the best of a wide class of many beautiful marine angelfishes. Gorgeous as a juvenile through intermediate sizes to gargantuan adult. Given an initially healthy individual, properly fed and housed, this is a centerpiece species able to be kept for years in captivity. Oh yes, if money is no concern, and a purplish behemoth is more to your liking, the Asfur or Arabian angel (Pomacanthus asfur), and Yellow-Band Angel (Pomacanthus maculosus) is also top choices. But for much less money up front you can have the equally large, spectacular and tough Koran.
Classification; Taxonomic Relations: The Koran is one of the seventy-four described species of the marine angelfish family, Pomacanthidae. The genus and family names include the Greek word acanthus =thorn, in reference to the prominent gill cover spine. Often caught in nets and hands. As a juvenile the Koran is easily confused with a plethora of other blue, black and white banded young angelfish species. Their other common name, semicircle angel, only applies to specimens of about one to three inches in total length. Older, larger individuals transform their irregular rear semicircles to sweeping lines. At four to seven inches they show what appears as Arabic script (hence the name Koran) in blue against black between blue lines on the tail fin. Some of the principal differences betwixt frequently encountered juveniles are highlighted in the accompanying photographs. Korans have four or five wider-distinctive white body band-lines that sweep back dorsally and ventrally. Other species of large angel's young have more striping that is more vertical (or more circular in the case of the imperator) and/or orange coloration which the Koran lacks. Adult coloration patterns are attained in a few years at a size of six-seven inches plus. The white stripes and blue fade to an overall pattern of dark spots on a yellowish-green background. Three inch juvenile, six, eight inch changelings below.
Distribution: Korans are found throughout the Indo-Pacific and Red Sea, and are likewise collected widely. The species is found foraging and hiding around coral and rocky reefs, not in open, upper waters or over sandy bottoms. You should provide some similar habitat. Selection; General to Specific: For most circumstances, Korans, like other large angelfishes, should be purchased as juveniles, but not babies. Very small individuals (less than two inches) should be avoided as they usually adapt poorly. Get at least a three inch specimen; and unless you have the time to expend and the money to gamble, not one over six inches. Larger specimens often time are problematical in terms of foods/feeding and behavior. Also of note, larger specimens (upwards of 16 inches) require systems of a few to several hundred-gallon capacities. There are a handful of important observational criteria to consider in picking out a good specimen. A prime one is apparent health as gauged by gill movement. A healthy individual displays regular, steady "breathing" of about once per second. Gill flukes, common and species-specific on these wild-caught fish, the effects of "gill-burn" from shipment/handling, poor present water quality, all can speed up the rate of gill movement. Avoid such angels. Instead choose one with full finnage and a full-body appearance, not thin in the head or stomach. Only buy angels that are alert interested in their environment, not skulking in a corner. These pomacanthids have a curious nature that mirrors their intelligence. The fish's color should be bright and uniform, showing no light spots, blemishes or pitting. Eyes must be clear and shiny. Ask to see the prospective purchase eat what you intend to feed it at home. Though most Korans that eat will live on, it's best to leave the specimen for weeks stay at the dealers holding it on deposit. Environmental Conditions; Chemical, Physical, Biological: Koran angels are more sensitive to poor water quality as marine aquarium species go. Excess organics often show as blotchy white-marked areas, and are directly positively correlated with ease of infectious and parasitic susceptibility. Temperatures in the low to upper seventy degrees Fahrenheit, lower to "normal" specific gravity (1.018-1.025), of natural or synthetic saltwater are fine. Effective protein skimming is a must have. Behavior Notes: All members of medium and large angelfish species are aggressive toward their own kind, other angels and similar-appearing fishes and are ideally kept one specimen to a tank. Moenich offers comprehensive advice on mixing angelfishes. Sometimes adding them at the same time, moving around parts of the habitat, disrupting territories, or bringing in ever-larger specimens can successfully mix these angels. This practice is not encouraged unless you have other facilities for separating them, should relations sour. In most cases other non-angel species are generally ignored; occasionally a Koran angel will become a bully, and require "rehabilitation" through removal or temporary isolation. Provide adequate hiding and escape spaces for tank-mates and observe your charges, as you should, daily. Feeding: This is the most critical area in keeping most angels and many other saltwater species. Koran's should be offered live and fresh foods and weaned from natural foodstuffs ASAP to survive and thrive. In the wild, Korans feed on algae and associated fauna primarily as juveniles; adults eat copious amounts of sponges, corals, and algae with the remaining bulk made up mostly of worms of all sorts, crustaceans and mollusks. They supplement this diet well in captivity with crustacean and other fresh and frozen animal foods. Opened, whole shellfish, squid, frozen and fresh crustaceans should be offered occasionally. Plant material/algae materials should be fed daily. Algae (Caulerpa, Ulva (sea lettuce), Nori and kombu from an oriental food supplier, et al.) and plant matter (spinach, zucchini, chard etc.) should make up a substantial part of their diet. Feed frequently, small amounts. Disease: Infectious, parasitic, nutritional and social diseases are a significant problem with this species. Beyond details already listed, careful handling, quarantine and freshwater dipping with or without admixtures are recommended. If necessary, copper treatments (best chelated types) are suggested for ridding pathogens. Summary: The Koran or Semicircle Angelfish, Pomacanthus semicirculatus makes an excellent first or beginner angel for aquarists with an adequately large system. It's easy to find, reasonably inexpensive; simple to maintain when purchased at the right size and fed properly, intelligent and long-lived. Bibliography/Further Reading: Allen, Gerald R. 1979. Butterfly and Angelfishes of the World. Vol 2. Wiley Interscience, New York. Emmens, C.W. 1972. Pacific angelfish. Marine Aquarist 3(1):72. Emmens, C.W. 1983. Large Pacific angelfishes. TFH 3/83. Fenner, Robert M. 1998. The Conscientious Marine Aquarist. Microcosm, VT. 432pp. Miklosz, John C. 1972. When is a Koran, not a Koran? Marine Aquarist 3(4):72. Moenich, David R. 1987. Angel food; the most important single factor in keeping marine angels healthy is a varied diet. TFH 6/87. Moenich, David R. 1988. Breaking the rules (on mixing angel species). TFH 3/88.
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