Most species of Acanthurus are found in the broad
area called the Indo-Pacific. One is found in the eastern Atlantic along
Africa, five in the Caribbean/western Atlantic.
They are mostly shallow water (1-100 meter depths),
rocky and coral reef dwellers.
Smaller species "only" get six to eight inches, the
largest ones to a couple of feet. Under ideal conditions the big ones
get that way quickly; growing a handful of inches a year.
Selection: General to Specific
There are four major criteria to consider when
judging the acquisition of members of this group; body conformation,
color, behavior, and time in captivity.
1) Body Conformation: Though appearance of a pinched stomach
is not of itself an accurate indication, healthy, freshly collected
specimens of tangs are well-fleshed. The upper body, above and behind
the eyes should not be "shrunk in", or show loss of color.
As per minimum purchase size for the genus, I would not buy any
specimen under three inches in length.
2) Color should be intense and uniform. You
should know that Acanthurus have different stress, fighting, nighttime
and reproductive markings and color phases; however prospective buys
should show no reddening, erosion, or blotchy discontinuities.
3) Behavior: Tangs that have been captured,
transported, acclimated and housed correctly are outgoing and curious
about their environment. Avoid hiding, sedentary and "spaced out"
individuals having "private parties" in dark corners.
The feeding "acid-test" super-applies to surgeons.
They should be eating a variety of foodstuffs at time of purchase.
4) Time in Captivity: I strongly suggest you
leave these surgeons a week or two at the dealer's for "hardening". Many
questionable animals are lost or otherwise "saved" in this way.
Surgeonfishes by and large fill a niche neither
occupied by permanent or transient reef predators, nor by constant
smaller denizens like the damsels. Except for the few that are more
meat-eaters, they are best described as the algae "lawnmowers" of the
tropics. You should keep their habit of constant food searching,
scraping and sorting lifestyle in mind when planning their care.
Acanthurus tangs require large amounts of tank space to be truly
happy. At adult size, fifty gallons per individual is not too much for
modest dimension species.
An important point here concerning the chemical,
physical and social environment of these fishes. Keep it optimized and
constant! pH should be buffered and maintained between 8.0 and
8.4., temperature kept in the seventies to low eighties F.
Keeping organic levels low to non-existent (no
ammonia, nitrite, maximum of 25ppm nitrate) through vigorous filtration,
under-crowding and frequent partial water changes is requisite.
Keeping Acanthurus surgeons presents a paradox in
maintenance. On the one hand they benefit from stable, aged systems with
diatom, green algal growth and detritus... on the other, they require
low waste loads and high dissolved oxygen.
Make no mistake about this last. Low gas solubility
results in loss of color and "gasping" behavior of tangs; panting,
laying on the bottom with rapid to slower to no gill movement. Make
their water movement and aeration vigorous.
For most hobby-size systems keeping one Acanthurus
tang to a tank is the best bet. Additionally, by design on your part
this fish be designated as the dominant animal in the system.
Except for the species listed as being relatively docile, other
Acanthurus should be held in constant suspicion, and watched carefully
if any new additions are to be attempted. Field studies bear out this
tendency toward agonistic behavior. The home range of these tangs is
several square meters; and rarely changing. Except when engaging in
"algae-searching" school "fronts" they chase out their own and similar
appearing and feeding organisms.
How to put this... put these tangs in "last and after
a while?" Acanthurus tangs should be placed as the final animal(s) due
to territoriality; and given the system's time to "age", stabilize,
accumulate detritus and grow some algae.
If you're going to try more than one Acanthurus
species or conspecifics, do put them in at the same time, make sure
they're of different size (and therefore decidedly not co-dominant), and
keep your eyes open for overt aggression.
Though they are of spiny-fin, proficient with their
razor-like peduncle scalpels, and can be ciquatoxic (poisonous for fish
or human consumption), surgeons are consumed by "the usual suspects"
predators. Measure those grouper and lionfish mouths twice before
Reproduction, Sexual Differentiation:
Acanthurus species show little structural or color differences
between the sexes. Well, in some the males or females are slightly
larger; and male coloring darkens and intensifies at the time of
breeding. Take a close look at photographs in the wild of large
Spawning by species in pairs and schools is tied to
lunar cycles, with two or more fishes making mad dashes, releasing their
gametes to the surface. These join to become planktonic young that float
about for a period of weeks to months. With luck and propitious currents
transformed individuals settle down onto a suitable reef.
Feeding/Foods/Nutrition: Types, Frequency,
Most Acanthurus surgeonfishes are celebrated algal
browsers, tooling along during all daylight hours scouring hard surfaces
for plant and associated food. Some members of the genus are known to
take considerable animal matter as well; A. thompsoni and A. mata are
principally zooplanktivorous. Nearly all will benefit from shrimp,
euphausiid, mollusk, other meaty foods included in their captive diets.
But let's not forget to emphasize surgeons' need to
nibble on greens. Unless you have but one tiny specimen in a very large
tank you'll have to purposely supply vegetable food daily. And more than
almost non-nutritive lettuce.
Where oh where can you get enough greens to satisfy
these aquatic lawnmowers? Maybe the oriental food section, or collecting
your own, or buying it through a bait shop (Ulva & Caulerpa, rhodophytes
(re) and phaeophytes (brown algae) are used for keeping bait organisms
These fishes need to be offered food frequently; in a perfect world,
small amounts all day long. An automatic feeder, stocked with an
appropriate mix of dry-prepared foods and set to maximum number of
feedings will get you there. As will store-bought or home-grown "algae
rocks". You can make these in most any salt-proof container with "old"
water change water and calcium carbonate based rock. Provide light and
Disease: Infectious, Parasitic, Nutritional,
If anything is more unfortunate than these fishes
penchant for fighting, it is their susceptibility to those twin
protozoan nemeses of captive marines, Amyloodinium and Cryptocaryon.
What's more to woe is the unsuitability of using copper compounds as
treatment. This common element in prepared aquarium remedies is of
course toxic to the algae and non-vertebrates possibly housed with your
tang(s); but it is also incrementally poisonous to the surgeons
Due to their essential gut fauna, and skin
characteristics there is no null zero-effect dose of copper compounds
with these fishes. Put another way, they are negatively impacted along
with the "bugs" you're trying to do away with when treated with copper.
What's an aquarist to do then? Number one, to exercise the usual
prophylaxes of quarantine and freshwater dips/baths in moving
Acanthurus. Secondarily, the use of facultative biological cleaners
(fish, shrimp) is promoted.
Nutritional disorders of tangs are so common a cause of disfigurement
and loss that we should mention them here as a disease that should be
avoided, and can be "cured". Much work has shown that vitamin A & C
deficiencies are a "cause" or co-cause in color loss and head and
lateral-line-erosion (acronym HLLE). This pitting may be sent into
remission with the feeding of these vitamins. Some aquarists tout the
virtues of specific chemical food supplementation; others rely on
natural or terrestrial veggie sources (broccoli, carrots...), blanched
Genus Acanthurus surgeonfishes span the range of
usefulness and adaptability for captive marine systems. Some are
relatively tough environmentally, and easy-going in terms of tankmate
behavior. Others have proven to be difficult for all but the most
attentive aquarists with large, optimized systems.
Consequential in their successful care is choosing
properly captured and transported specimens, providing adequate space,
aged, highly circulated and aerated water, and constant provision of
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