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What would Billy Shakespeare say, what's in a name? Plenty when it comes to the common or 'lay' terminology of some fishes. Let's talk about the Surgeonfishes alone. Can you tell me which three species are called "blue" tangs? (at least the Atlantic A. coeruleus, the fabulous powder-blue, A. leucosternon, and the Indo-Pacific Paracanthurus hepatus; the last also called the hippo, palette, regal, yellow-tailed blue...). How about the three fishes termed 'striped' surgeons? How many sailfin tangs do you know? Ho-boy, if there ever was an argument for scientific names.
In this piece we'll strike for a closer understanding of just two very similar appearing species of surgeons whose common and scientific names are way too often interchanged in the trade. For purely intellectual reasons this mis-identification might bug you, but as they say on late night infomercials; "Wait, there's much more". The two species in question look alike, yet are very different in likeliness to do well in captivity. Based on handling hundreds of specimens, I'd peg their relative potential at aquarium survival for three-plus months at a hundred times more likely for one over the other. For specifics on these two surgeons and news you can use on the group in general read on.
Classification: Taxonomy, Relation With Other Groups
There are some six genera and about seventy two species of surgeons; many are prominent reef and aquarium members. Additionally, the family includes several important human food fishes.
For higher taxonomy, information on the Acanthurids relation to other fishes, please see the references cited by Winterbottom, 1993. For the purpose of our article here, let's confine ourselves to describing the color, differences between the species at hand:
Acanthurus nigricans, (formerly A. glaucopareius) which we will call the powder-brown surgeonfish/tang is an overall varying brown with a white patch under the eye. The dorsal, anal and ventral fins are black with blue edges. The base of the dorsal and anal fins is graced with a brilliant yellow; their tails are white with a vertical yellow bar.
Acanthurus japonicus ("Ah-kan-thur-us ha-pawn-ick-us") will refer to as the white-faced surgeon/tang is similarly marked and colored with the following notable differences. The white-faced tang is adorned with a red stripe on it's dorsal that starts one third back and extends to the end. Check out the white patch under the eye, it's larger in A. japonicus, extending all the way to the mouth, hence the name white-face (sometimes white-cheek). Body-shape wise the white-face is decidedly more oval than the powder brown as well, but you tell me, could you tell these two apart if you didn't have both on hand for comparison? And what's the big deal anyway? They're both good looking.
Ah, but one is a historically poor feeder, most dying within a few weeks of purchase; the other a very hardy aquarium species. Both are sold under each other's names, often for similar cost, and there indeed, is the rub. Yes, you do want to know how to tell one from the other, and to purchase the white-faced A. japonicus, and avoid A. nigricans.
The powder-brown is widely-distributed over the vast mid-Pacific area called Oceania, including Hawaii; it also is found along the East Pacific from Baja, Mexico to South America. It's range overlaps that of the white-faced surgeon in parts of the tropical Indo-Pacific, but displaces it between New Guinea and Australia.
The vast majority of both these fishes are collected and shipped from Indonesia and the Philippines. Please see the section titled 'Selection' for my opinions on the origin you might pick up the best specimen.
Both to approximately twenty centimeters (eight inches) total length in the wild, about fifteen centimeters in captivity.
Selection: General to Specific
The following actually applies well to all marine aquarium fish purchases, but is slanted to the tang family.
1) Beware of mouth problems. Tears, any redness disqualifies a purchase. Surgeons vary in the extent to which they scrape and rasp algae and related matter for food. Their snouts get smacked easily in the processes of capture, transport and handling. Once the mouth is infected, the fish is generally a goner.
2) Color discrepancies can be a real warning sign. Surgeons blanch, white-out, get mottled when frightened/stressed; and when sleeping. The only way to know what a good specimen looks like is to study; use a good reference, observe enough specimens, talk with fellow enthusiasts.
3) Glancing behavior. All tangs pick at and scratch their bodies at times at the bottom. Some, like the hippo, etc. tang, Paracanthurus hepatus spend a great deal of time just lying on their side. But there 'normal' and 'abnormal' amounts of glancing, and too much is indicative of poor water quality, infestation... some other bad situation. How to know how much to expect? See #2 above.
4) Respiratory rates and movements. Breathing should be 'regular' for the species, size, and not labored or short...
5) Optimum size at purchase. For these species, no smaller than three inches, four to five is ideal.
6) Body thickness. Very important, especially for specimens that originate from the Philippines and Indonesian Islands. Many of these will not have been fed for very long. Tangs eat a lot, and very frequently, make that constantly. They 'get thin', and 'give up' eating at some point. When looking at a prospective buy, look at it head-on. It should be full, rounded in body contour, and not concave, in particular in the head.
7) Patience. No, not the fish, you. Wait for one to two weeks for new arrivals at your supplier to adapt or pass on, i.e. croak. Put up a decent deposit and leave the specimen 'on hold'. Professional retailers endorse this activity.
8) Sources are important: for the powder brown species, if you must try it, get one from Hawaii, Baja, Tonga, Christmas the Marshall Islands... Not the Philippines or Indonesia..
Collecting Your Own
These tangs, like most of their family are captured by driving them into a well placed barrier net, being hand netted from there. You can too by purchasing or making suitable semi-invisible nets, traveling to the site, securing necessary permits...
These surgeons live in coral outcroppings with prominent drop-offs and brisk currents. Could you make something like this?
Chemical/Physical I consider the bird-like swimming behavior of tangs to be analogous with another canary characteristic; they are good bio-assay organisms. If something dire is amiss with your water quality, surgeons will show it best in the short and long term. Immediately, they darken, blanch, become inactive, breath rapidly and shallow. What to do? Check your water, do a water change, move the livestock?
Surgeons enjoy clean, low organic load, high oxygen solubility water. Keep the pH high and consistent, in the low eights. Nitrates as low as practical, ten parts per million or less.
There continues to be the "what came first, chicken/egg question/discussion" concerning "hole in the head, lateral line erosion" (environmental) disease. Is "it's principal cause the protozoan Hexamita necatrix, poor water quality, vitamin C or other nutrient deficiency? The simple answer; yes, probably some/all are important. So do quarantine/dip new arrivals, monitor and optimize your system's water, and by all means utilize vitamin supplements. Oh, and a side note re the chicken/egg thing. If birds are derived from Ornithischian dinosaurs which were egg layers, doesn't that mean...?
Another important note regarding substrate and nutrition. You might provide a little fine sand for the tang's use in aiding digestion. They ingest this in the wild, sometimes to the extent that you can see it through their body wall. A little in a (sic) glass dish will do fine.
Brisk and complete. Is there such a notion as too many turns over per hour for marine filtration? Make sure and provide plenty of aeration if you're a tang lover. They are active, breathing, eating, defecating machines, that are accustomed to full gas saturation. Typically they are the first to expire with rising temperature, power outage, mechanical air loss...
At least a fifty gallon size system. Some studies have measured seven plus square yards per tang on the reef. Now that's a tank!
Very. One to a tank, unless the system is huge; several hundred gallons. If you're as tang-crazy as astronauts try surgeons of different body shapes. Congeners, species in the same genus generally slash it out.
Allow me the space to give a 'plug' for the use of 'ditherfish', probably damsels among others, to keep the peace. Having a few of these aqua-poodles goes a long way to defuse and diffuse aggression.
Tangs are best put in as some of the last fishes, after the system's been up a few months. This usually assures greater chemistry, physics and social stability. Though they are not typically pushovers, Surgeonfishes do not appreciate changes in the make-up of their home, tankmates and decor. Their is anecdotal evidence of tangs dying from having coral et al. shifted around the tank, or other fishes being removed.
Most tangs, or at least these two, leave most everyone else alone and are in turn not bothered as adults. I've seen small tangs used as hook and line baitfish in Hawaii among other island groups, and observed them attacked and swallowed in captivity by the usual suspects (basses, triggers, etc.) but this is rare.
There are some surgeon exceptions, like the clown tang, A. lineatus that are bad-boys; we'll discuss them some other time.
Reproduction, Sexual Differentiation/Growing Your Own:
All known surgeonfish spawning observations indicate they are group spawners; at dusk skimming up near the surface, releasing gametes that convert to planktonic larvae, floating to and through the open seas.
For development history of a related species, Hawaii's Manini or Convict Tang, Acanthurus triostegus see Randall's citation.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
The story with porky tangs in the wild is that they are constantly foraging. All take vegetable material, of course including our two here. Additionally, meaty foods are needed. Frozen brine shrimp is a great base; others should be offered, not just dried flake foods.
My personal outrage here concerning the use lettuce, romaine, iceberg or glow-in-the-dark, I don't care; they're worthless nutritionally to Surgeonfishes. I even give the boot to chopped spinach. Get real, go to the oriental food section of your food-store or other specialty outlet and buy algae processed for human consumption. These are readily available and as far as fish food costs go, cheap. Dried Nori and kombu are relished by tangs. Alternatively, making, growing "algae-rocks" is simple enough to supplement your charges diets with live material.
Feeding strike? Don't panic. Patience will win out with an otherwise healthy specimen. Live brine shrimp is a sure winner. Concerning live. B.S., make sure to freshwater rinse/soak these for a few minutes to reduce the incidence of introducing parasites.
Disease: Infectious, Parasitic, Nutritional, Genetic, Social
Tangs are susceptible to those scourges of tropical reef disease, the protozoans Cryptocaryon & Amyloodinium (Oodinium). They are frequently the first in a tank to show signs of infestation, and the first to effect a cure with copper-based medications. I'll go on record here advising against continuous copper treatment of these (and all other) fishes. The tangs digestive system micro-fauna has been studied quite a bit, and found to be important and consistent in it's make-up. Chronic copper treatment/toxicity may well account for substantial 'anomalous' losses. Avoid these problems best by quarantine/dip, secondly by treatment in a separate vessel.
One of the most frequently encountered queries we hear in the pet-fish industry touches on the ethics of what is offered: Why do 'they' offer (the organism in question) under different names? Knowing that (the organism in question) doesn't do well under captive conditions? After many years (thirty plus) in the aquatic nature business I can assure you that 1) No, it's not some grand conspiracy to cheat the Western consumer. 2) No, not another mean-spirited lesson meant to impress the diminishing value of the dollar on you. 3) But yes, the state of sophistication of the collectors, shippers, wholesalers, retailers and other go-betweens. That is, it's about as good as we all can do collectively, at this point, and 4) The fact that we all, as consumers, are/have been willing to pony up our hard-earned cash for what's offered.
I don't like it, the waste and inefficiency, and I don't think you should either. Become a more intelligent consumer, and cast your votes/dollars for livestock that lives. In this case the white-faced tang, A. japonicus. If you want a challenge, know that you're getting one with Acanthurus nigricans.
Campbell, Douglas G. 1979. Fishes for the beginner. A guide for the new marine hobbyist, pt III. Tangs. FAMA 1/79.
Herre, Albert W. 1928. Philippine Surgeonfishes and Moorish Idols. Philippine J. of Sci. 34(4) pp 403-478. Avail./TFH
Emmens, C.W. 1985 Surgeonfishes. TFH 1/85.
Randall, John E. 1975. Hawaiian fish profiles. Aquarium Digest International 3:2, 1975.
Sands, David. 1994. Superb surgeons. FAMA 10/94.
Winterbottom, R. 1993. Myological evidence for the phylogeny of recent genera of surgeonfishes (Percomorpha, Acanthuridae), with comments on the Acanthuroidei. Copeia 1993(1):395-414