It’s considered taboo to
keep large angels, butterflyfish and triggerfish in coral reef
aquariums, but over the years I’ve become more experimental
regarding fish in reef aquariums.One fish that always intrigued me is the crosshatch
triggerfish (Xanthichthys
mento).Based
upon its natural habitat and feeding behavior, I suspected that it
would fare well in a reef aquarium and ignore most sessile
invertebrates.The
only reason I haven’t tried one until recently is because I’ve
never been able to find a juvenile specimen.Adult crosshatch triggers can reach 12 inches in length,
and most of the fish that I’d seen for sale have been in the 6
to 8 inch size range.I’m
a firm believer in purchasing juvenile fish.I’ve always found that they transport better and adapt
easier to life in captivity.Adult fish often have narrow dietary preferences.They can be more territorial and wary than juvenile fish,
which makes it more difficult to introduce adult fish into an
existing community of reef fish.
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A
spectacular adult male Crosshatch Triggerfish displays in
front of the glass in an aquarium at the Reef & Fins store
in Stamford, CT.This
fish is nearly 7 inches in length.
All
triggerfish belong to the order Tetraodontiformes, which includes
the closely related filefish, pufferfish and boxfish.Triggers are members of the family Balistidae.The common name “trigger” comes from a unique
characteristic of the first dorsal spine.It can be “locked” into an upright position and held in
place by the second dorsal spine.At the first sign of danger, triggerfish bolt for the
nearest reef crevice and “trigger” their built-in locking
mechanism.Once
secured in place, they’re near impossible to remove.
Triggerfish
are typified by a tough leathery skin and strong jaws that contain
incisor-like teeth.They
swim by rippling their soft dorsal and anal fins.This unusual swimming motion allows them to swim backwards
as well as forward, which can be advantageous when moving in and
out of coral crevices.Triggerfish
generally make good aquarium inhabitants because they’re hardy,
disease-resistant and easy to feed.Many possess a certain “personality,” which further
endears them to aquarists.
The
crosshatch trigger has the typical triangular shape of triggerfish
when its fins are erect.It
looks more like a torpedo when it’s on the move.Similar to other members of the genus Xanthichthys,
crosshatch triggers are sexually dichromatic.The male has a more intense yellow background color on the
body and sports a red-rimmed tail, as opposed to the female, which
has a yellow-fringed caudal fin.They are easily distinguished.Both sexes have blue radiating lines on the face and black
lines that criss-cross along the body, hence the name
“cross-hatch.”
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:Pinktail Triggerfish (Melichthys
vidua) are closely related to triggers of the Xanthichthys genus.Unlike
most triggers in the family Balistidae, they have a relatively
mellow disposition.
Crosshatch
triggerfish are distributed throughout the tropical and
sub-tropical Eastern and Western Pacific Oceans but occur mostly
around smaller isolated oceanic islands.They can be found in large schools in open water, usually
at depths of 90 feet and greater.They feed exclusively on passing zooplankton.This partly explains their relative rarity and expensive
cost in the aquarium trade.They
can be kept singly, in pairs, or in groups of one male and two or
more females in the aquarium.I would not try to keep two males in anything but the
largest of aquariums.
Similar
to most mid-water planktivores, crosshatch triggers are not
finicky eaters and will consume most aquarium fare.Their diet should consist of predominantly meaty seafoods,
such as chopped whole shrimp, squid, larval silversides, and mysis
shrimp.Chopped krill
is a particularly good food item because it provides beneficial
carotenoids that help maintain the bright pigmentation in these
fish.Similar to other reef fish that feed from the water column,
crosshatch triggers should be fed a few times a day in order to
maintain body weight.If
a fish develops a pinched abdomen, it’s not getting enough food.Once starvation reaches the dorsal musculature, it’s
usually too late for the fish to recover.
Crosshatch triggers are active fish that can grow to a large size;
therefore I recommend a minimum of a 55 gallon aquarium for a
single specimen.Pairs
and groups should be maintained in nothing less than a 90 gallon
aquarium.They require areas of open swimming space as well as places
to hide at night or when frightened.A small area of reef rock set up along side an open expanse
of sand will suit the crosshatch triggerfish just fine.Since they occur at greater depths, it may take a while for
these fish to adapt to the brighter lights in coral reef
aquariums.If the
plan is to maintain them in a live rock/fish-only type setup, then
I suggest using lights with a preponderance of blue.Temperature is not critical, but I would err on the cooler
side of reef temperatures (75-78 degrees Fahrenheit).This species frequently occurs around sub-tropical islands,
such as Midway Island in the Northwestern Pacific and Soccoro
Island in the Eastern Pacific.Around tropical islands, they occur at greater depths where
the water temperature is cooler and more stable.
A healthy female Crosshatch
Triggerfish (Xanthichthys
mento) poses for a picture in one of the sale tanks at the
Reef & Fins store in Stamford, CT.This fish is approximately 6 inches in length and
shares this aquarium with a larger male specimen
A juvenile Crosshatch
Triggerfish (Xanthichthys mento) swims past a Tridacnid clam in the author’s
500 gallon reef aquarium.It is a bold and active fish and makes great addition
to a reef aquarium.The
specimen pictured here is approximately 3.5 inches in length.
The
up-slung mouth, protruding jaw, and eyes set atop the head give a
further clue as to the open-water feeding habits of the crosshatch
triggerfish.With
that anatomical structure, it’s near impossible to feed on
benthic invertebrates.This
is why I thought they would make a good and interesting addition
to my coral reef aquarium, and so far all is well.After a rude welcome from my existing power-blue tang (Acanthurus
leucosternon), everyone settled down and the juvenile
crosshatch trigger became part of the community of fish in my 500
gallon reef aquarium.It
eats very well and completely ignores all corals, clams, and other
sessile invertebrates, just as I expected.
The
ornery disposition of most triggerfish is absent in the
crosshatch.It’s a
relatively mellow fish that tends to ignore its tank mates.It will mix well with most other reef fish, although I
wouldn’t suggest introducing small Pseudochromids, or similar
bite-sized fish, into a tank of adult crosshatch triggers.They could be mistaken for a special food treat.On the other hand, existing small damsels, wrasses and
basslets are generally ignored.
As I mentioned earlier, I greatly believe in
purchasing juvenile specimens for the aquarium.This is especially so with crosshatch triggerfish.Adults tend to be very shy and can take quite a while to
adapt to captivity.If
they are going into an aquarium of aggressive fish or larger fish,
I suggest a period of quarantine first in order to introduce the
trigger to aquarium conditions and prepared foods.Crosshatch triggerfish are generally hardy but I would
insist on seeing a fish eat before purchasing it.These are not inexpensive fish and I wouldn’t want to
make that kind of mistake.I
have seen adult crosshatch triggers refuse food and waste away in
aquariums.Perhaps
they suffered internal injuries from being brought to the surface
too quickly.
If
you want to try your hand at something less exotic and less
expensive than the crosshatch triggerfish, the similar blue-throat
trigger (Xanthichthys
auromarginatus) and sargassum triggerfish (Xanthichthys ringens) are good alternatives.These fish are easier to find and generally hardier than
the crosshatch trigger.They also don’t grow as large.The related genus, Melichthys,
offers additional possibilities, such as the popular pink-tail
trigger (M. vidua).Similar to the crosshatch triggerfish, all these triggers
feed on zooplankton passing in the currents along outer reef
drop-offs.They should not pose a problem with corals in an aquarium
and tend to have a more placid disposition than many of their
triggerfish brethren.
Bluethroat Triggerfish (Xanthichthys
auromarginatus) are a less expensive alternative to
Crosshatch Triggerfish (Xanthichthys
mento).They
feed from the water column and generally ignore sessile
invertebrates.
