Paracanthurus hepatus (Blue Tang)
Of the more than ten-thousand species of
marine fishes, only a few hundred regularly grace our marine
aquariums. Size, ease of capture and transport, availability
of air-freight are some of the limiting factors on the
supply side; beauty, adaptability to captive conditions, and
hardiness are some of the prominent demand criteria.
The surgeonfish family garners more
than it's share of these top slots as choices for marine
systems. Several of its members have proven aquarium-tough.
Disease resistance, food acceptance, brilliant color and
markings are high marks for quite a few tang species. In
particular two, the yellow Zebrasoma, and yellow-tail
blue tang, Paracanthurus hepatus are highly prized.
The latter is used extensively in the hobby and trade; so
robust as to be a "standard" in the aquarium service
Surprising to me however, many
aquarists are hesitant to stock Paracanthurus,
stating low success in keeping them alive, and early loss to
"hole in the head disease", or "anomalous" causes.
Yellow-tail blues that have been
collected, housed and selected properly are excellent
long-term livestock; most of the problems associated with
their loss are initial over-stress, lack of nutrition, and
poor water quality. Here are my observations, borrowed
facts, ideas and methods concerning this species.
Relation With Other Groups
The six genera and seventy two or so
species of surgeonfishes (family Acanthuridae) are classed
within the largest Order of true bony fishes, the
Perciformes. The suborder that contains them (Acanthuroidei)
includes the difficult Moorish idol (family Zanclidae),
venomous rabbitfishes (family Siganidae), the delightful
scats (Scatophagidae), the spadefishes, Ephippidae, that
currently include the batfishes (Platax), and an
obscure foodfish called the louvar (family; you guessed it,
These six families of fishes are
bundled together taxonomically as acanthuroids for their
sharing of an equal number of technical internal
characteristics. They are all marine, generally herbivorous
with moon-shaped tail fins, and their juveniles pass through
a salient transparent planktonic larval stage in called an
The surgeonfish family itself
comprises six genera, all with more than one species except
our fish du jour. Paracanthurus can be distinguished
from all other tangs by its distinctive coloration, and if
you look closely, the possession of only three soft pelvic
fin rays (others have five).
The monotypic genus Paracanthurus
is most nearly allied with Zebrasoma; and for
practical purposes the yellow-tail blue shares most of its
husbandry parameters with the sail fin tangs.
A quick mention re the "other" blue
tang(s); you'll run into at least the Atlantic Acanthurus
coeruleus. It's a beauty too, but obviously a seperate
Natural and Introduced Range
Paracanthurus hepatus, has many common
names; it is sometimes known as the regal, or flagtail
surgeonfish; aka the hippo or palette tang in the west. The
last is my favorite, as the palette tang does exhibit the
brightest artists' blue, black and yellow. It ranges widely
throughout the reefs of central and Indo-Pacific, to
Africa's east coast, singly or in small schools.
To about a foot total length in the
wild, half that in captivity.
Selection: General to Specific
Index of fitness,
is a fisheries measure of relative chubbiness, body
circumference divided into length. A healthy tang is
decidedly well-rounded. Pinched in, narrow profile
individuals should be left in the ocean, or dealer's tanks.
Too many times the "reason" (cynical quotation marks mine)
for hollow head and flankedness is tied directly with how
long the specimens have been starved since capture. This
should be days, not the ofttimes weeks in reality. Don't buy
skinny marines period.
Feeding and general behavior;
healthy, well-adjusted (yep, a psychological term) surgeons
are active, curious, anxious eaters on most foodstuffs. Seek
out fish that are cruising about, interested in what's going
on around them, sampling what have you as food.
most palette tangs are collected in the vast waters of the
Philippine and Indonesian Islands; these have not proven to
be the better specimens. For what it's worth (and it does
cost more, and is well justified), Paracanthurus
hailing from New Caledonia, Christmas, Fiji and Marshall
Islands et al. are superior. How to tell where yours is
coming from? There's always taking a gander at your dealer's
invoice; and a skilled eye can discern the more robust,
better colored specimens from these "other" locales. My
advice; pay the extra to get better livestock; encouraging
better capture, holding and shipping practices elsewhere.
mentioned here as a criterion to not select by. These
fish do change intensity with stress and mood; but quickly
and unreliably. Besides, there are subtle to larger color
and marking differences with locality and size that are hard
Collecting Your Own
Nowhere is the palette surgeon in
great abundance, but I have collected them in Guam,
Indonesia and the Philippines in the following fashion.
Large individuals usually are solitary, smaller one's may be
found associated in a group of ten or twenty in and around a
large coral head or black coral stand that they take refuge
in on a divers approach. A type of net termed a fence, mist
or barrier is set up ten to thirty feet away in a U-shape. A
retreat away from the area with the holed-up
Paracanthurus is feigned and the specimens are chased
and pressed against the fence net on showing signs of
leaving their coral nest.
Talk about a paradox; the palette tang
does best in a well-established system, one that's been up
for a few months; but requires "bright" clean water, devoid
of measurable organics. How do you get and keep this
mystical "high water quality"? Two words; filtration and
Circulation itself should be
turbulent; the more motion in the water the better. Surgeons
appreciate high oxygen gas concentration. An efficient
protein skimmer (if possible with an ozonizer) is absolutely
necessary; as is over-sized biological and chemical
filtration. There should be no detectable color to your
water (test some in a tall glass against a white piece of
paper, compared with a sample of tapwater).
Paracanthurus may be easily mixed with
others of their own kind and any other fishes that will
leave them be. They are best exhibited in large (hundreds of
gallon) systems with vertical groupings or walls of rock and
coral skeletons to provide refuge.
The palette surgeon gets my vote as
the least territorial member of its family. Though they will
"posture" and "shake their caudal spine" in a threatening
way to challengers to their favored hiding or swimming
route, Paracanthurus are wont to actually inflict any
real damage to conspecifics or other tankmates.
This is one of those species that are
better off not being purposely quarantined; put another way,
IMO (in my opinion), the stress induced via isolation and
re-moving Paracanthurus is generally more harmful
than the risk of introduction of some contagion. I would run
newcomers through a preventative bath/dip of pH adjusted
freshwater and promptly place them in the main/display unit.
To alleviate within-species
aggression, if you intend to keep more than one, it is best
to introduce all palette tangs at the same time. If need be,
make later additions larger than extant members.
Other than small, i.e. planktonic
invertebrates and algae, Paracanthurus leave other
aquatic life alone. There are other fishes that pester them
to distraction though. Be wary of "the usual suspects,
including other tangs, large basses and angels, triggers...
these can bother your palette to non-feeding.
A quick note here concerning this
species propensity for lying on its side, and sidewise
"glancing" against the systems substrate. This sort of
behavior is natural and to be expected. Do be on the look
out for external parasitic problems should yours seem to
"scratch too much", and if need be, move the item your tang
seems "stuck in" rather than attempt extricating it.
Frequency, Amount, Wastes
Stomach contents analysis of wild
Paracanthurus show that this fish is omnivorous,
consuming benthic and planktivorous invertebrates and
attached algae. Aquarium diets need be diverse, fresh and
encompass some nutritious "green" material on a daily basis.
Further, your close watch to ascertain
that your palette(s) are eating is called for. As feeders
they can be driven away by bullying tankmates, and sulk away
to dangerous thinness. In my estimation, a lack of nutrition
and outright food are the key reasons for loss of these
This is the darkest element to keeping
the palette tang. Paracanthurus are quite susceptible
to crypt, (amyl)oodinium, and other infectious and parasitic
outbreaks common to captive marines. They are particularly
liable to an erosive condition termed HLLE, "head and
lateral line erosion". There is growing evidence that this
symptom of this bilateral gross pitting and bodily
disfigurement is principally due to a lack of nutrients,
mainly the vitamins C, A and D; but there are still
advocates that a/the root cause of HLLE is stray voltage,
and/or the protozoan Octomita necatrix, and/or "poor
It is my anecdotally derived opinion
that all these factors play their part in the expression of
HLLE. Given that the species is inclined genetically to this
disposition, resolve to keep yours well-fed, in an
appropriately set-up and maintained system. Avoid specimens
showing signs of erosion as young, and don't give up should
yours start to fade and show signs of pitting. Enriched
foods and improved conditions have shown to reverse such
The many-named blue tang,
Paracanthurus hepatus makes an excellent aquarium fish;
active, gorgeously beautiful and long-lived: stipulated that
1) A stable optimized environment;
particularly high water quality and brisk circulation.
2) Foods, including some greenery
daily, and evidence that the fish is amply feeding.
3) Selecting healthy specimens;
perhaps the most obvious, yet often missing link in keeping
these fish alive.
the permission of Robert (Bob) Fenner webmaster of WetWebMedia
Photos: top photo by G.J.Reclos; other photos by