Tangs, Surgeons and Doctorfishes, Family Acanthuridae, are amongst the most commonly kept marine specimens. Every Aquarist "worth their salt" can identify a Naso, Yellow, Hippo/Palette/Yellow-Tail Blue Tang. Surgeonfish use in our hobby is well warranted; their numerous and easy to catch on the worlds tropical reefs, and several species in the family live comfortably under captive conditions.
Well, one might ask, "What about the others; what's wrong with them?" An answer might involve the fact that some in the genera Naso, Prionurus, just get too darn big, requiring aquariums of hundreds to thousands of gallons at adult size. Other reasons abound for the unsuitability of additional species, and reciprocally, a lot of acanthurids are too drab to be of interest to saltwater aquarists. But what of the topic of this piece, the surgeons of the genus Ctenochaetus ("ten-oh-key-tus")?
They're attractively shaped, colorfully marked, and interesting behaviorally... why doesn't the industry import them more often? Are they uncommon in the wild? Are they too hard to catch? The honest answers; Ctenochaetus aren't rare or difficult to herd into barrier nets; but hobbyists have not had "much luck" historically in keeping these tang species alive. The avoidable reasons this is so (capture, handling, transport, and feeding) I will lay out here, and offer suggestions to improve their longevity.
Classification: Taxonomy, Relation with Other Groups
One of six genera of acanthurids, Ctenochaetus comprises nine of the seventy-five or so described species of Surgeonfishes. Specialized mouths and teeth (cteno-chaetus means "comb bristle" define the genus' members. Unlike other surgeons that have rigid, attached dentition, Ctenochaetus have movable, individual, bristle-like teeth. Coupled with a protrusible, outreaching mouth, these fishes use this unusual feeding device to sort and remove interstitial fauna, scrape soft algae, and "detritus" of nutritive value from rock and substrate.
Some pertinent notes regarding the four species of Ctenochaetus occasionally offered in the trade:
Largely tropical Indo-Pacific, two species reaching north eastward to Hawaii, two to the eastern Pacific. Some to the African Ocean, one species ranges to the Red Sea.
They grow to a maximum length about six to ten inches depending on species.
Selection: General to Specific
1) Size: at purchase; small specimens, less than three inches overall length, have high mortality rates. If you're going to risk one of less dimension, I'd definitely leave it at the dealers for a couple of weeks and be assured that it was feeding before taking it home.
3) Behavior: the element of "brightness", curiosity in the environment, normal swimming and evasiveness cannot be discounted. Buy well-adjusted specimens.
These fishes, though slow moving, shy and retiring, require large amounts of tank space to be truly happy. Additionally, that space should have a propitious amount of hollows and surface area, for hiding and foraging.
A fine gravel bottom and lots of calcium carbonate based rock will go a long way in providing diatom growth, other detritus for inorganic and organic nutrition.
Bristletooth Tangs live in the brisk current environments of steep reef faces. As such they are accustomed to being buffeted by waters that are high in oxygen and low in soluble wastes. These parameters may be matched in pursuing one of two strategies: either super-fastidious filtration and control, or live-algae, low stocking-rate. The latter is my choice.
Through less than tidy housekeeping and culturing live rock growth, a good deal of nutrient is reconstituted as food and readily removed by Ctenochaetus. This is one situation where you should avoid vacuuming the gravel of the system; instead allowing the livestock to circulate loose matter around.
Higher pH's are called for (8.0 and 8.4.), and temperature for all species in the seventies degrees Fahrenheit.
As stated emphatically elsewhere these surgeons are openly detritivorous, deriving biological and mineral material from scrounging around rock and sediment. Hence, it is important to not be meticulous in removing such material.
Rigorous circulation is appreciated, from power-heads or other fluid-moving pump(s). Lighting that favors algae growth as well.
Though Ctenochaetus are generally easy going with other fishes, (including different genera of surgeons stipulated that they are of widely different size), they can be, or become sheer terrors with members of their own kind or tankmates. Even though often found in pairs or even schools in the wild, they are best kept one to a tank unless the system is HUGE.
Small Ctenochaetus are highly regarded for use in "reef" systems. They make for well-adapted additions will not attack invertebrates that are useful for algal control.
A comment re that so tang-like defensive mechanism, in Ctenochaetus a single peduncular spine; these are potentially lethal weapons, able to render a sharp laceration to tankmates and unwary aquarists. Don't be fooled by these fishes' casual movements and smallish size; they are capable of doing serious damage. Want more? There are accounts of acute pain and swelling from puncture wounds caused by Ctenochaetus dorsal and anal fin spines. Keep your eyes on your other livestock, and hands if/when in the tank.
The vast percentage of members of this surgeon genus is lost through rough handling and transport. You must take great pains to ensure that the fish you buy are not net and/or bag damaged, and consequently protected from such.
Professional collectors recognize the dangers in thrashing bristlemouth tangs in coarse, rough hand and barrier nets. They should be as sensitive to the dangers of miss-shipping them as well. If at all possible, avoid netting these fishes altogether, instead drive them into submersed bags, not hard specimen containers. Further eliminate the possibility of damaging their protruding mouths by using bag sizes and water volumes sufficient for turning.
Per the comments offered on habitat and feeding, your Ctenochaetus should be placed as the last of fishes to the system.
Large predaceous reef fishes like basses, eels, and etc prey upon surgeons. Keep them separately.
Reproduction, Sexual Differentiation:
Debelius (in ADI) gives some observations on spawning of C. striatus. In a group, some individuals changed from dark brown to light beige. Becoming more active, three to five would dart to the just under the surface, releasing their gametes. Debelius and Baensch (1994) state that C. strigosus spawns only in pairs.
The sexes are indistinguishable externally.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
Due to mouth traumas and typical non-feeding for several days covering capture, initial holding, shipping and probable wholesale redistribution, getting Ctenochaetus (as well as all marines) to feed in short order should be a top priority.
Maybe a better name than "hairy" is "comb" bristles in reference to Ctenochaetus teeth. It occurs to me that this is more descriptive of these fishes feeding habits; their sucker-like mouths and movable teeth sift and lift loose materials. They do not nip off hard, large foodstuffs like other tangs.
My favorite "gimmick" with these fishes is to utilize an algal covered "feeding stone" as a site for engendering food-taking behavior. I encourage you to do the same; placing (I use a big "turkey" baster) waterlogged dried, fresh, and/or defrosted frozen food as fine material amongst the algae.
For surgeons, the "hairy toothed" tangs benefit from much more than a diet heavy in greens does. A high protein (forty percent plus), even purposely vitamin enriched diet shows in well-fleshed and colored specimens.
As stated elsewhere, these fishes are grazers that do well only in under crowded, less-than tidy tanks, with plenty of rock and detritus to pick over. Randall (1955) recorded up to 90% inorganic sediment in analysis of gut content of C. strigosus from the wild.
Ctenochaetus tangs tend to arrive in "clean" condition. Though other authors endorse copper medications with them, I would rather urge you to use freshwater dips and quarantine for the two-pronged benefits of eliminating infestation and hardening your new specimens.
The dismal survival rates for Ctenochaetus are more a function of poor capture, handling, transport and feeding problems imposed by their captors, than these fishes suitability as captive specimens. Given attention to preventing damage to their sensitive mouths, a not too fastidiously clean environment, and provision of adequate foodstuffs "hairy toothed" Surgeonfishes make beautiful, long-lasting aquarium additions.
Burgess, Warren E. 1977. The chevron tang. TFH 3/77.
Burgess, Warren E., Herbert R. Axelrod & Raymond E. Hunziker III.1990. Atlas of Aquarium Fishes Reference Book, v. 1 Marine Fishes. T.F.H. Publications, NJ. 768pp.
Campbell, Douglas G. 1979. Fishes for the beginner, A guide for the new marine hobbyist, Parts three and four, Tangs. FAMA 1,2/79.
Debelius, Helmut. Undated. Interesting information about surgeon (sic) fisch- III The Ctenochaetus genus. Aquarium Digest International #31.
Debelius, Helmut. 1993. Indian Ocean Tropical Fish Guide. Aquaprint Verlags, Germany.
Debelius, Helmut & Hans A. Baensch. 1994. Marine Atlas. Mergus, Germany. 1,215 pp.
Fouda, M.M. El Sayed, A.A. & Z.T. Zaki. 1988. Reproductive biology of a Red Sea Surgeonfish, C. striatus (Quoy & Gaimard, 1824). Proceedings of the Sixth Intl. Coral Reef Symposium. Vol. 2 pp. 679-683.
Guiasu, Radu C. & Richard Winterbottom. 1993. Osteological evidence for the phylogeny of recent genera of surgeonfishes (Percomorpha, Acanthuridae). Copeia 1993(2):300-312.
Jones, Lawrence L.C. 1988. Care and maintenance of tangs in captivity. Part one: Food and feeding. FAMA 10/88.
Lobel, Phillip S. 1984. The Hawaiian Chevron tang, Ctenochaetus hawaiiensis. FAMA 3/84.
Nelson, Joseph S. 1994. Fishes of the World. 3rd Ed. Wiley.
Nelson, S.G. & S.D. Wilkins. 1988. Sediment processing by the surgeonfish C. striatus at Moorea, French Polynesia. J. of Fish Biology 32(6) 1988:817-824.
Purcell, S.W. & D.R. Bellwood. 1993. A functional analysis of food procurement in two surgeonfish species, Acanthurus nigrofuscus & C. striatus (Acanthuridae). Env. Biol. of Fishes 37(2) 1993:139-159.
Randall, J. 1955. A revision of the surgeonfish genus Ctenochaetus, Family Acanthuridae, with descriptions of five new species. Zoologica 40:149-165.
Randall, J. 1975 Hawaiian fish profiles. ADI 3:2, pp 12,13
Randall, J.E. 1988. Three nomenclatorial changes in Indo-Pacific surgeonfishes (Acanthurinae). Pacific Science 41:54-61.
Sands, David. 1994. Superb surgeons. FAMA 10/94.