Ask the WWM Crew
|Please visit our Sponsors|
N. hexacanthus, the Blacktongue Unicornfish. A slender coolish green bodied fish with a bright navy blue tail. Neither males nor females develop a horn; but do have black tongues!
Largely Indo-Pacific; from Hawaii to Indian Ocean, up into the Red Sea. Unicornfishes associate with steep coral and rocky reefs; several occasion into deep open water.
The smaller Naso species attain a foot and a half total length; the largest ones approach three feet. Not small aquarium fishes.
Selection: General to Specific
1) Body Shape & Size: Have you ever seen full-size tangs, either diving in their domain, at a public aquarium, or an underwater photo? They're outright porky. The stomach areas of healthy surgeons may be pinched in, but they should be otherwise well-fleshed in appearance. Speaking from first hand experience, I can tell you that these marines often go unfed from collection to the wholesaler for days to weeks; this is wrong, and is too often the cause of later mortality.
Know also that these fishes bodies can look very different with growth; becoming much more elongate and longer-of-horn.
Size at purchase I've lumped here to illustrate the link between it and body conformation. Smaller than 4" Naso tangs rarely live adapt to living in captivity, unless they're un-starved and placed in a setting with unlimited access to food. My advice? Buy larger (four plus inch) Unicornfishes. Can you get one that's too big? Sure, depending on the spatial assets of your set-up. I have seen more-than-a-foot Naso (lituratus) "streamers" (with long, trailing ends to the upper and lower margins of their caudal fin), placed with success in humungous systems. The same fish would die "mysteriously" of "behavioral problems" put in a six foot system. at purchase I've lumped here to illustrate the link between it and body conformation. Smaller than 4" Naso tangs rarely live adapt to living in captivity, unless they're un-starved and placed in a setting with unlimited access to food. My advice?
2) Swimming Behavior: Healthy, happy Unicornfishes are out and about during daylight, briskly moving horizontally along the length of their system. Sulking, hiding specimens should be refused. It may be that they've just been/are being cramped space-wise, but these fishes can be pushed over the edge psychologically to where they don't recover.
4) Source Location: The best Naso lituratus, bar none, come out of the Red Sea; the second, the Hawaiian Islands. Talk to your supplier regarding the relative merits of added cost versus the likelihood of success of where they can get you surgeons.
5) Color: I want to mention as not being very important. The patterns and hues of Unicornfishes quickly change with for reasons apparent and not. They have fright, sleeping (on the bottom), feeding, fighting and more mood shifts. Should one be off-color at the moment, don't automatically count it out.
A note regarding moving members of the genus Naso: Be careful; if not for the fish, for yourself. These are powerful fishes that all too often launch themselves missile style when cornered or netted. They're skin is thick and tough, and those scalpel-like processes really sharp. Better to net guide would-be-caught fish into large double-bags underwater.
Environmental: Conditions Habitat
These tangs require large amounts of tank space for swimming exercise and expression. Four feet is a minimum length system for a small specimen; to house one for long, six feet would be better, much larger best. These animals range over large areas on steep reefs, picking at attached algae; as adults zooplankton becomes much of their food. At night they assume cryptic coloration and settle into the reef at rest. Can you replicate something of this physical environment?
Naso tangs are celebrated as being tolerant of a wide range of water conditions; standard "fish tank" only parameters are fine. I find it a good idea to encourage surgeon placement last in an established system to 1) ensure stability, 2) allow for some algal growth and detritus accumulation for food, and 3) reduce the likelihood of inter-specific aggression.
Whatever form is used, it should be accompanied by brisk circulation. Unicornfishes are big, fast-moving fishes that require high oxygen concentrations; their water cannot be moved about too vigorously.
Given an adequately large system, Naso species are generally the mellowest of surgeonfishes. Perhaps it's the confidence of their speed or sharp lateral keels, but they get along with most everyone. Agonistic behavior on other tankmates behalf cannot be totally discounted however; I have seen triggers and large angels that would torment a Unicornfish to it's loss.
Take care to consider relative sizes, size of the system, and the order of introduction of livestock to the system, when thinking about your fish's individual personalities.
For practical purposes, unless you have a huge (hundreds of gallons) system, it is best to house just one Naso tang to a tank. Also, due to their liking for environmental and chemical stability, optimally place the Unicornfish as your last fish.
A Naso in a reef tank? Not likely. They're too big and rambunctious, and much too likely to chomp on prized invertebrate and algal livestock.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
Once trained on aquarium foods, Unicornfishes become "eating machines"; getting them up to through that initial period is the real challenge. Live adult brine shrimp is a great initiator for small tangs. For greens, live marine algae, attached or free-floating are ideal; dried algae, flakes, and terrestrial greens are all secondary to these. On the issue of lettuce etc... I would encourage you to abandon this non-nutritive placebo for cruciferous vegetables (broccoli, Brussels sprouts), even cabbage, carrots or chopped spinach would be better. Rinse, blanch in boiling water to make it easier to ingest.
In the wild Naso spp. are herbivorous as young; accepting more zooplankton with age. As captive Unicornfishes become acclimated they greedily take all foods. Meaty types like larger shrimp and Euphausiids, worms of all sorts should be supplemented with daily greens.
Infectious disease of Unicornfishes is easily warded off through freshwater dips and quarantine procedures. Transient copper treatments will cure them of ectoparasites.
Nutritional disorders should be mentioned. Much work has shown that vitamin C (and others) deficiency is a "cause" or co-cause in color loss and lateral-line-erosion. This pitting may be sent into remission with the feeding or addition of this transient vitamin. These avitaminoses are best prevented rather than "cured" by varying nutritious foods and possibly supplementing diets.
Social "disease"; apparent "sulking" should not be ignored. Find and cure the cause(s) ASAP; generally too small a tank, bullying by a tankmate, change in decor (move it back)...
Now you know there is more than one Naso; and they all take a BIG tank. If you've got the space, you're now equipped mentally to pick out a viable specimen and house it reasonably. Get yours to feed, but not too much; otherwise you'll have to seal in the front door and fill the house with seawater to accommodate the unicornfish's growth.
Anon. 1993. response to an inquiry re numbers of species of Unicornfish. Sea Frontiers. 3,4/93.
Campbell, Douglas G. 1979. Fishes for the beginner, A guide for the new marine hobbyist, Parts three and four, Tangs. FAMA 1,2/79.
Collins, Steve. 1995. Dietary control of HLLE in blue tangs. SeaScope, Summer 1995.
Debelius, H. 1975? Useful information on surgeon fish. Aquarium Digest Intl. #29, pp 31-33., #31, pp 28-29.
Debelius, Helmut. 1993. Indian Ocean Tropical Fish Guide. Aquaprint Verlags, Germany.
Debelius, Helmut & Hans A. Baensch. 1994. Marine Atlas. Mergus, Germany. 1,216pp.
Jones, Lawrence L.C. 1988. Care and maintenance of tangs in captivity. Part one: Food and feeding. FAMA 10/88.
Maisey, John G. 1996. Fossil surgeonfishes. TFH 4/96.
Meyer, K.D., Paul, V.J., Sanger, H.R. and S.G. Nelson. 1994.
Effects of seaweed extracts and secondary metabolites on feeding by the herbivorous surgeonfish Naso lituratus. Coral Reefs 13(2):105-112.
Nelson, Joseph S. 1994. Fishes of the World. 3rd Ed. Wiley.
Nelson, S.G. & Y.M. Chiang. 1993. An exploratory analysis of the food habits of herbivorous surgeonfishes (Acanthuridae) from
French Polynesia. Proceedings of the Seventh Intl. Coral Reef Symposium, v. 2:920-926. Univ. of Guam Press.
Randall, J.E. in, Smith, M.M & P.C. Heemstra (eds.). 1986.
Smith's Sea Fishes. Springer-Verlag, Germany. (Acanthuridae) pp 811-823.
Randall, J.E. 1994. Unicornfishes of the subgenus Axinurus (Perciformes: Acanthuridae: Naso) with description of a new
species. Copeia 1, 1994:116-124.Randall, J.E. & L.J. Bell. 1992. Naso caesius, a new Acanthurid fish from the central Pacific. Pacific Science 46(3):344-352.
Sands, David. 1994. Superb surgeons. FAMA 10/94.
Smith, J.L.B. 1966. Fishes of the sub-family asinae with a synopsis of the Prionurinae. Ichthyological Bull. Rhodes Univ. 32:635-682.
Spencer, Gary C. 1973. The tang and I. Marine Aquarist 4(4):73