How many Surgeonfishes in the genus Acanthurus do you know? There are Powder Browns (A. nigricans (nee glaucopareius) and A. japonicus), the Powder Blue, Atlantic Blue, Achilles, Orange-Shoulder, Oriental/Pajama/Lineatus... any others? Hey, no cheating by looking below. All told there are some forty described species in the genus; two "mimics" often mistaken for Dwarf Angels!

Some Acanthurus make hardy captive specimens, others have a dismal aquarium history; most are too poorly known to be judged as yet. Here I'll present my version of who's "good", "bad" and unknown; how to select and maintain the tangs in the genus Acanthurus.

Classification: Taxonomy, Relation With Other Groups

The Surgeonfish family Acanthuridae comprises six genera and about seventy two species. Many are important food and aquarium fishes. Think of the other genera that include the yellow and other Zebrasoma, yellow-tail blue Paracanthurus, various Naso, and less known Prionurus and Bristlemouth (Ctenochaetus) Surgeonfishes in addition to the Acanthurus. What do they have in common?

All Surgeonfishes are laterally compressed covered with very small scales giving their bodies a leathery appearance. They have long continuous dorsal fins, and small terminal mouths with fine teeth. What really distinguishes the whole family though is the presence of one or more spines on the caudal peduncle (the part of the body right before the tail fin), hence their scientific name from the Greek, acanthus = "thorn". With a twist of the tail these spines are used to as a formidable weapon when needed.

Modern classification schemes divide the six genera of Acanthurids into two subfamilies (names ending in "inae") and three tribes (ending in "ini").

The subfamily Nasinae, with one genus (Naso, the Unicornfishes) and seventeen species have two anal fin spines and three soft pelvic fin rays. Several have a frontal "horn" protuberance that gets larger with age. Four branchiostegal (gill supports) rays.

The subfamily Acanthurinae, the rest of the Surgeonfishes, bear three anal fin spines and five soft pelvic fin rays. Five branchiostegal rays.

Tribe Prionurini; one genus (Prionurus), six species; rarely offered in the trade. Have 3-10 non-retractile bony plate "scalpels" on their caudal peduncles.

Tribe Zebrasomini; containing the genera Paracanthurus (one species, the yellow-tail blue), and Zebrasoma of seven species.

The Tribe Acanthurini; genera Acanthurus and Ctenochaetus can be discerned from each other by the six species of Bristlemouths (Ctenochaetus) peculiar long, comb-like teeth. 

Genus Acanthurus ("Ah-Kan-Thur-Us") Species; The Good, The Bad, and The Unknown

Dear Reader, in checking through the voluminous worldwide pet-fish literature which are the anecdotal accounts of hobbyist attempts at keeping this genus, I am struck by several opinions that greatly vary from my own. After handling tens of thousands of these fishes, diving and talking with collectors and public aquarium personnel hundreds of times these are mine... My criteria for "good" species are ones that more than half live three plus months after arrival. "Bad" ones, have behavioral problems and/or a mortality of more than 50% in the first month.

"Good" Acanthurus (One's That Generally Live):

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Acanthurus chronixis  See below under: Mimic Surgeonfish

Acanthurus coeruleus Bloch & Schneider 1801, the Atlantic Blue Tang; though not as dazzlingly beautiful as the other two "Blue Tangs" (Paracanthurus hepatus & Acanthurus leucosternon) this Caribbean surgeon makes a fine aquarium addition. One of a handful of Acanthurus that are overall yellow as juveniles, the Atlantic Blue Tang stays small enough for modest sized aquariums.

Acanthurus coeruleus (Juvenile)	Acanthurus coeruleus (Midsize.)	Acanthurus coeruleus (Adult)

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Acanthurus dussumieri Valenciennes 1835, the Eyestripe or Dussumier's Surgeonfish. This is a highly variably colored fish. Some are drab gray, whereas some I've seen from Hawai’i sported brilliant yellow around their body margin with beautiful royal purple highlights. This surgeon is more like the genus Ctenochaetus in its feeding habits, sifting sand and detritus in addition to algae scraping. Specimens off Maui, in an a hobbyist tank and a profile of one off Queensland, Australia. To eighteen inches long in the wild.

Acanthurus fowleri  de Beaufort 1951.  Fowler's Surgeonfish. Western Pacific: Philippines, Indonesia, Papua New Guinea, Solomon Islands, and off northwestern Australia. To: 45 cm. Photo by SaraM at SDC.

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Acanthurus japonicus (Fowler 1946), the White-Faced Surgeonfish; also sold as a/the Gold-Rimmed or Powder-Brown Surgeon, confusing it with A. glaucopareius (nigricans) (see below). A. japonicus has a much larger white eye patch. Ranges from the Philippines to Japan and is relatively hardy. A nigricans, the Powder-Brown at right for comparison (Nuka Hiva, Marquesas pic).

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Acanthurus maculiceps (Ahl 1923), the Freckle face Surgeon. To some 16 inches in the wild, about half this in captivity. Indo-West Pacific. A more common import the last couple of years in the West. Pricy but beautiful and hardy.

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Acanthurus mata Cuvier 1829, the Elongate or Mata Surgeonfish. Indo-Pacific; Red Sea, eastern African coast to French Polynesia, Japan, GBR, Micronesians. Similar to A. xanthopterus lives almost exclusively on zooplankton. Long misidentified as A. bleekeri. To 50 cm. One off of Gili Air, Lombok, Indonesia, another in Mabul, Malaysia.

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