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'Lets just say it's one of the 'Triggers' of my addiction.'
Most marine aquarists, whether it be a relatively new amateur or seasoned veteran professional, remember their first moment of marvel when they decided to jump the gun and dive, sometimes literally, into the world of marine life. Growing up in Southern California I was quite fortunate to be exposed to marine life, and the ocean in general. As a child I maintained a relatively well 'working knowledge' of our marine life, that all locals who interact with the ocean should for safety reasons. A formal education or a directed study of the animals however inspired little interest in me, despite my family 'pedigree' in diving, sailing and swimming. The awe moment for me, surprisingly happened about 3 miles inland from the coast at a now defunct wholesaler in the row of famous importers just adjacent to Los Angeles International Airport. As a child a family friend of mine was giving us a tour when she stepped over to feed a rather large,12 inches (~30.5cm) by my offhand estimation, Balistidae, specifically a Clown Trigger (Balistoides conspicillum). I was in amazement of how the animal recognized her approach to the tank and almost 'begged' for the food that it associated her presence with. Before this incident the notion that a fish could have personality was pretty foreign to me. For most people their foray into aquatic keeping of any kind, and especially marine husbandry, is inspired by the visual, usually an animals color and/or beauty. While I consider one of trades most recognizable fish, the Clown Trigger, an attractive species, it's looks had almost nothing to do with my interest. Prior to this experience I had never associated intelligence with a fish, let alone be able to attribute one with K-9 like pet qualities or even better anthropomorphize them. And while I initially decided to pursue experience and education in other forums of marine life (our local temperate denizens), it was certainly this Trigger, well, triggered by addiction.
We've all heard one Balistidae horror story or in the case of those of us who've ever helped Bob Fenner answer reader queries at WetWebMedia.Com - a thousand or more. As glorified as they are in the trade for their flamboyant color patterns and individualistic personalities, they are equally if not more so vilified for their ability to take over and literally level a system from the inside out. Still it is that beauty and penchant to be boisterous that makes them one of the most popular family of fish in our hobby. Many of the animals from this species make superb single specimen displays where their robustness can be fully enjoyed as they pose no threat to any other creatures, save for perhaps their caretakers hands now and again. However realistically most aquarists aren't willing to do this and thus take a spin of the roulette wheel by introducing a Balistidae into a community or even more boldly at times an invertebrate/reef aquarium. As most advanced aquarists will tell you, there are very few guarantees in this hobby (or in life for that matter) some bets are statistically safer than others. That finally brings us to the topic at hand, the genus Xanthichthys, whose range, diet and behavioral patterns makes them perhaps not ideal candidates, but candidates nonetheless for inclusion in home community and reef aquaria, especially in comparison to some of the other genus' like Balistapus and Balistoides.
Balitids in General: Taxonomy, Anatomy, Behavior and Range
'Always identify the target before you pull the 'Trigger''
forty-one members of Triggerfish, family Balistidae, hail from the
order Tetraodontiformes which also includes filefish, boxfish,
procupinefish and even the ocean sunfish. Tetraodontiformes in
greek is derived from the words 'tetra,' meaning four and
'odous' meaning tooth or tooth bearing and finally
'forma' which is at is sounds, form or shape. They're
given this name because all of them have four bones in their small but
powerful jaws. These bones are often modified into fused teeth, giving
them a very avian 'beak' like appearance, others have teeth
that resemble K-9 like incisors. These teeth are built for one
thing, preying on other reef denizens that, through natural selection,
have developed literally hard defenses such as shells and spines -
usually invertebrate life. These animals are experts at attacking
and making a meal of animals such as crustaceans, mollusks, bivalves,
echinoderms and stony cnidaria life that are often off of the menu for
family of fish are aptly named for their use of Balistform locomotion.
Unlike many other bony fish, they do not use their caudal fins as
a primary means of propulsion, using it in rare short bursts for
'escape speed.' Instead Triggers have large oval
compressed bodies using undulatory movement of their dorsal and anal
fins. Due to this anatomy these fish lack in overall speed but
more than make up for it in maneuverability, which is important in the
coastal rocky reefs they typically inhabit in their circumtropical and
somewhat subtropical ranges. Balistidaes derived their more
common name, Triggerfish from the three spines making up their
dorsal fin. The first spine on the dorsal fin can be raised and locked
into position by the second spine which must then be decompressed
(like a Trigger) in order for the first to fall back flush. The animal
uses this function to secure itself in a rock crevice in an attempt to
prevent would be predators from pulling them out. Other defenses
for the animal include thick skin; rhomboid shaped scales that overlap
to armor the fish. Additional defining characteristics include
independently moving eyes to identify giving them an increased field of
view to identify would be predators or prey. Balistidaes sizes
range almost as much as their color patterns the smallest of the genera
can top out only at four inches (10.2 CM) while the largest species can
attain a whopping forty inches (100 CM). These fish are demersal
spawners digging pits and laying their eggs on the substrate. This
necessitates guarding of the nest by the mother in order to ensure a
successful spawning and woe be it to the reef denizen, or human diver
for that matter, that unknowingly wonders into her territory.
In the wild,
behaviorally speaking, these fish display a wide amount curiosity and
many species are rarely intimidated my fish three and five times their
own size. They're ability to move and use rocks as tools and
learn from previous experiences, committing them to memory, shows a
level of intelligence that is much higher than many of the other
denizens they share the reef with. When disturbed or agitated, or
even perhaps as a warning to others nearby, these fish can vocalize a
deep clicking sound. This clicking noise at times sounds like the deep
grunting of a pig, alluding to the common name officially given to
Rhinecanthus (and also to Triggers in general by many locals) in
Hawaii, Humuhumu nukunuku apua'a (which pretty much translates to
water pigs with needles). As experienced divers and aquarists
will tell you their level of 'personality' (and aggression) not
only varies from species to species, but also from individual to
individual. One of the other behaviors that this family has the
capacity to exhibit is spitting, long time aquarists are well familiar
with the Triggers ability to literally spot water at their owners out
of the tank.
population of Triggerfish is within the tropics of the Indo-Pacific and
Atlantic, though some species are found within the lower tempered
subtropics. Most members of the family prefer to stay within the
rocks and reefs of coastal areas, though there are a few exception
species, which exhibit pelagic, open ocean swimming/dwelling,
behavior. The aforementioned species, some of which belong to the
genus we're here to discuss; Xanthichthys, express more
planktivorous feeding habits and are thus less suited to captive
adaptation (but we'll get into those specifics later
Genus Xanthicthys: A broad overlook of the Genus
'No such thing as a safety on these Triggers, but this is as close as you'll get.'
genus of Balistidae is made up of five species, there is however some
controversy and confusion with this number. Many divers and
aquarists have mistaken certain color variations in Xanthichthys
auromarginatus and Xanthichthys mento for being an additional member of
the genus. Moreover, there have also been reported hybrids of
Xanthichthys lineopunctatus, likely also involving Xanthichthys mento
from the Christmas Islands (Several of these have infrequently shown up
in Wholesale importer tanks here in Los Angeles, in particular Quality
Marine). Some hobbyists believe this Christmas Island Trigger to
be a sixth member, dubbing it Xanthichthys 'Dorsal-Punctatus.'
While the hobby may discern 'X. Dorsal-Punctatus' or the
'Christmas Island Trigger' as an additional genus member for
price points or identification purposes, the Scientific and Ichthyology
community has not. We'll get into the specifics of these five
'official' species later on.
The range of
Xanthichthys is somewhat more limited than the rest of the Balistidae
family as a whole, four species of the genus have it's populations
limited to the Indo-Pacific while one is confined to the
Atlantic. The genus is more likely to inhabit deeper water and
pelagic areas away from the coastline as well, making their range not
completely accountable for. For example, Xanthichthys Caeruleolineatus
was only identified in the Hawaiian Islands as recently as 1993.
Furthermore juvenile populations of many Xanthichthys have been found
up to 500 miles (805km) away from the coastline and certain species are
not uncommon at depths of 500 feet (153m) plus.
One of the first
differences in the appearance that many notice between Xanthichthys and
the rest of the Balistidae genus is their proportionately smaller
mouth. For many home-aquarists this smaller mouth is an
indication of this animals more subdued aggression tactics, but
it's also a great insight into the animals dietary needs. Due
to their more 'oceanic' swimming patterns, Xanthichthys rely
primarily on free floating zooplankton, some species almost
exclusively, earning them the broad label of planktivores in many
circles. It should be noted though that this does not preclude
larger specimens of the genus from attacking smaller motile crustaceans
or even sessile inverts at times, yes it's rarer, but again there
are no guarantees.
One of the other
interesting virtues of Xanthichthys is that two members of the species
distinctively exhibit sexual dichromatism, the other three much less so
or not at all. As far as breeding goes, despite their pelagic
range, most sources still point to Xanthichthys Triggers still being
demersal spawners like the rest of the Balistidae family. Some
reports have indicated that certain populations of Xanthichthys are
willing to lay eggs within the reef or rock-work, rather than burrowing
nests in the substrate, but none allude to the release of gametes in
the open water column. Furthermore most current evidence
points to all Xanthichthys triggers as being dioecious. What this
means is that unlike many other reef fish, Xanthichthys are born with
their genders already determined when they are born; males are males,
and females are females, neither can revert to or transform into the
It is the
feeding behavior and range discussed here, disassociating them (but not
completely excluding their interaction with) from sessile
invertebrates, larger crustaceans and echinoderms, in comparison to
other Triggers, that makes them so sought after in home community and
reef aquaria. Unfortunately these same qualities also make them
somewhat less suitable for captive life by comparison.
A wild specimen of X. ringens on a reef in
the Bahamas. Photo by Bob Fenner
A wild specimen of X. ringens on a reef in the Bahamas. Photo by Bob Fenner
Species Specific Xanthichthys Notes
'This is my gun err
fish...there are many like it but this one is
X. auromarginatus, known to most as the blue jaw trigger (blue throat and gilded trigger are also common local names) is typically the most regularly imported of the Xanthichthys genus. Of the five species in the Xanthichthys genus, two display distinct sexual dichromatism and X. auromarginatus is one of them. Most of the specimens you will see available in your local dealers tanks will undoubtably be mature or maturing males. Females are not collected as often due to their lacking the blue pigmentation on the lower jaw and head, as well as the green to yellow hues that often line the caudal, dorsal and anal fins of many matured males. It is also not uncommon to pairs offered for sale in the aquarium trade, and if you plan the addition of more than two, to your aquarium, I suggest you purchase them as such. Having said that this species tends to be slightly more social, or at least tolerant of it's own kind, than other members of the Balistidae family, they can at times be seen congregating in the open water column at the edge of reefs just before drop-offs usually feeding on their primary food source; zooplankton. Almost always found in association with an established reef, this species is found in depths ranging from 30 to almost 500 feet (aprox. 10-150m) with a range that spans from the Indo-Pacific, including large populations in Hawaii, and all the way to Eastern Africa. Up to 12 inches (aprox. 30cm) in total length though full grown adults in the wild are more common at 10 inches (aprox. 25cm), while captive specimens tend to top out just over 8 inches (aprox. 20cm).
X. caeruleolineatus, commonly called the blue lined, outrigger or goldenback trigger, is rarely seen by divers and aquarists alike due to them rarely inhabiting or venturing into water shallower than 175 feet (53m). The animal commonly inhabits depths as deep as 675 feet (aprox. 205m) As such not even the extent of this species range is fully known by the scientific community, as was mentioned earlier, it was as only as recent as 1993 that this animal was confirmed to be a resident of the Hawaiian islands. Their secretive and deep nature makes viewing them in their natural habitat and collecting them difficult. Furthermore animals that inhabit niches of this depth have a strong propensity to suffer from poor collection, as they are brought to the surface too quickly. This leads to a high mortality rate during collection and the time immediately ensuing it. All of these factors contribute to their lack of availability, to be blunt targeting and capturing them for the ornamental marine aquarium trade, is simply not cost effective. Specimens that are collected are usually done so accidentally by commercial trawling. Suffice to say if you do happen to see this species in your local dealers tank, it will have a price tag that compliments it's rarity (An anecdotal note, the last specimen I saw just over 1,000 US dollars). This animal does exhibit some sexual dimorphism but not enough to reliably distinguish genders by eye sight alone.With a potential size of 14 inches in the wild (aprox. 35cm), most specimens collected are usually around the nine inch (aprox 23cm) mark, and rarely grow much more than that in aquaria.
While not known to inhabit as deep of depths as X. caeruleolineatus (Blue lined Trigger), X. lineopunctatus, or the Striped Trigger, is just as a rare sight for divers and thus enters the aquarium trade very infrequently as well. When found this species is usually associated with offshore reefs and atolls, inhabiting depths from 75 feet (aprox. 23m) to 170 feet (aprox. 51m) with a range spanning the Indo-pacific into eastern and southern Africa. Occasionally specimens are caught in drive-in nets by collectors, but they aren't the targeted prey. Sexual dimorphism in this species is negligible, and not worth noting as even an offhand way to distinguish genders. To a foot (aprox 30cm.) in length in the wild.
X. Mento, known by most as the Crosshatch Trigger, is easily one of the most stunning looking denizens in the trade, inspiring amazement in both non-hobbyists and long time veteran aquarists alike. Though still found in association with shallower reefs, groups can routinely be found venturing away, congregating in the open water column to feed. Inhabiting depths of 10 feet (aprox 10m) to 220 feet (aprox 100m), this animal has a wide range being found in the tropics and even sub-tropics. It's been observed that specimens inhabiting the warmer tropical climates tend to be found at deeper depths, while their sub-tropic counterparts tend to be more likely to stay in shallower water. One explanation is that this animal prefers slightly cooler temperatures of about 74 -78 degrees Fahrenheit (23-25.5c), which is still within the tolerable range for many other tropical denizens. In aquaria I have seen them housed in tanks in the 80 degree Fahrenheit (27c) range in the long term, multiple years. From these anecdotal observations I can not say whether or not the animal is harmed longterm from being housed in these conditions, but I would be willing to say it's much less of a death sentence than say housing a temperate species like Lythrypnus dalli (Catalina Goby) in reef aquaria. Like it's cousin X. auromarginatus (Blue Jaw Trigger), X. Mento also displays distinct and easily recognizable sexual dichromatism. Males display a stark yellow, almost neon, body coloration with a red tail and marginal blue line, females display a less bright but also attractive slate gray to blue body and tail. Both animals have each scale outlined in black giving them the classic crosshatch appearance. Though not as staple in the trade as X. auromarginatus, X. Mento is seen relatively regularly in the trade, typically offered as lone males or in pairs with a price tag that matches their awe-inspiring appearance. Reaching a maximum of 11 inches (30cm) specimens topping out around 9 inches (23cm) are much more common.
X. mento juvenile in an aquarium. Photo by
X. mento juvenile in an aquarium. Photo by Bob Fenner
X. rigens, the red tail or Sargassum trigger, is the third of the five Xanthichthys triggers that makes it's way into the trade with any predictable regularity. Certainly the most pelagic of the genus, it derives it's common name from juveniles of the species that are found hiding within floating Sargassum in the open ocean. Adults tend to stay slightly closer to the coast but are still known for being a deeper water reef fish, typically inhabiting slopes and drop-offs usually well below 100 feet (30m). While they prefer inhabiting these depths, unlike X. caeruleolineatus they are much more prolific residents in their respective locales. Adults of this species are also far less selective in their diet than others of the genus, and large groups can be seen foregoing their typical planktivorous diet in favor of small crustaceans and echinoderms (usually sea urchins). This is mostly an Atlantic species being found as far north as the Carolinas in the United States, to Bermuda and down to Brazil. These animals display no reliable sexual dimorphism, and sexing by eyesight is unreliable at best but more like impossible. Sought after in the aquarium trade because of it's desirably small average maximum size of 9-10 inches (23-25cm) it is unfortunately, of the regularly imported Xanthichthys species, the one that adapts the poorest to captive conditions, no doubt because of it's more pelagic behavior.
An aquarium specimen of X. ringens. Photo by
An aquarium specimen of X. ringens. Photo by Bob Fenner
(Hybrid) Xanthichthys 'dorsal -punctatus' a.k.a. The Christmas Island Trigger
Relatively recently, within the last 24 to 30 months, a few interesting individuals have shown up in dealers tanks from the Christmas islands, not with any regularity, but certainly more than they have in the past. Most believe these to be a hybrid of Xanthichthys mento x Xanthichthys lineopunctatus, while some hobbyists have insisted that the lack of mutation in it's appearance points to it being it's own species, as there tends to be more variation in the hybridization of species. The scientific community has not yet recognized this as a new species and there is much debate concerning it's genetic make-up. At any rate the commercial side of the hobby does denote a difference, as it does with many other animals that are hybrids or the same species (ex.. Naso Literatus Tangs vs Blonde Naso Literatus). On the very rare chance that one of these makes it into a local dealers tank it will likely be labeled X. 'Dorsal-Punctatus,' (for the markings behind the head running parallel to the dorsal fin) or simply as the 'Christmas Island Trigger.'
'What's the 'Trigger' point? Hope for the best, plan for the worst.'
Most Xanthichthys may not be pelagic by the
strict definition of the word but they certainly have more of a
propensity to venture outside of the reef and into the open water
column in comparison to other reef denizens. The relevancy of
this information however, is that like other pelagic animals, they tend
to suffer more in the rigors of collection and transport to captivity
as well as adjusting to captive fair immediately after
collection. For this reason I would only consider animals that
have been in dealer tanks for a minimum of two weeks. I
understand that due to the infrequency of some of these animals you may
want to purchase them at the first opportunity, speak to your dealer
about putting a deposit down to reserve the animal while not taking it
home. Larger adult specimens that are 8 inches (20cm) or larger
tend to be, well like grandma, set in their ways and much more
selective as to what they'll accept as part of their diet.
Likewise juveniles under 3 inches (7.5cm) in length who are used to
feeding exclusively on live free floating zooplankton also have
difficulty in adjusting to a captive diet as well. If possible I would
select 'maturing' or 'teenaged' specimens in the 3.5 to
6 inch (9cm - 15.5cm) range. Be sure you observe the animal
feeding on frozen or prepared fair in the dealers tank as well, animals
that have sunken, pinched sides, or are uninterested in food are to be
avoided. Likewise don't necessarily write off animals
that are in a bare-bottom, sparsely decorated, holding tank and has
attempted to wedge or 'trigger-lock' itself into the corner by
laying on the bottom. This isn't an automatic sign of poor
health, as mentioned earlier Balistidaes will often 'lock'
themselves into the rock work for rest or when scared. The animal may
simply be expressing it's natural behavior as best it can with what
it has to work with and Xanthichthys tend to be more reclusive than
other members of the Balistidae family to begin with. If
attempting to buy a pair, be sure to ask your local dealer if the
animals were collected together (they can often even call their
importer to verify this), as local dealers have been known to
'force' pairs together for more marketability. The
success rates between pairs collected together in the wild is much
higher than that of artificial pairs that are attempted between captive
'If you're going to pull the trigger, make sure you have the right ammo'
Acclimation to Captive Life
Unlike a lot of their rough and tumble cousins, such as Balistapus undulatus, the Xanthichthys genus has more trouble adjusting to wide changes in water chemistry. Keeping this in mind, and being that most hobbyists experience death in their livestock during the receiving process, acclimation should be done slowly and methodically. Animals should be acclimated in a dark holding or quarantine tank with at the most, ambient light. If the animal is received via overnight shipping, the temperature is likely to be below that of the acceptable range, begin by floating the bag in the holding tank or in a bucket of actual tank water for no less than half an hour. Once this is complete, begin by opening the bag and adding small amounts of tank water in regular intervals (example six ounces or 175 milliliters every 15 minutes) or better yet a slow but continues gravity drip from the intended holding/quarantine tank. Continue this process for no less than 2 hours, and if possible without scaring or stressing the animal, add aeration to the acclimation bag or bucket. Due to their sensitivity and track record in acclimation I prefer not to dip Xanthichthys in freshwater or medicated baths proceeding their introduction into quarantine. Once quarantine is complete if you wish to 'dip' the animal before introduction into the display, do so then. New specimens are often fickle and nervous, and reclusive behavior for days or even weeks is normal, you can encourage them to be more adventurous by initially using a subdued lighting arrangement and feeding small but frequent amounts of finely chopped foods.
While certainly smaller than many of the other Balistidaes available in the trade, due to their penchant for open water swimming, I would not place any adult Xanthichthys species in a tank measuring smaller than 48x18 inches (122cm x 46cm) at it's base surface area. Likewise while it's necessary for them to have some sort of structure to retreat to (live rock preferably) portions of the aquarium should be left open for swimming and feeding that resembles their natural behavior. In addition while Balistids have the ability to lock themselves in the rock work they must speed up their respiratory pattern in order to cope as most evidence points to them being forced induction breathers. This means in order to maximize their oxygen intake they must swim to forcibly move water past and through their gills, as such you should provide ample strong and turbulent water flow in their habitat to assist them in this.
Too often ignored by aquarists, a proper varied diet is of the utmost importance for captive livestock, and Xanthichthys not only aren't an exception but perhaps even a personification of this. Too often specimens are offered fair in blatant contrast with their primarily, or in some cases exclusively, zooplankton diets. When preparing the diet for Xanthichthys, it may be more prudent to look at the diets of other planktivores such as Anthiinae, rather than compare them to other Balistidaes. In fact the stomach contents of some dissected specimens of Xanthichthys auromarginatus have indicated that they feed solely on pelagic, free floating, copepods. Live freshly hatched artemia can be a great way of enticing new or shy specimens into feeding, but switching to a diet of varied prepared fair as soon as possible should be a priority. Small fair such as frozen mysis and chopped krill are readily available though you can vary the diet of your trigger even further by making it's food yourself. By utilizing a blender you can purchase and offer your trigger a diet that it would not normally eat in the wild such as squid, scallops, large crustaceans, even other fish and don't be afraid to mix in nori sheets, spirulina and other vegetable matter of a marine origin. The reason for this being you can not accurately replicate the exact diet of the animal in the wild and by doing this you diminish the chances your specimen will suffer from a nutritional deficiency. As planktivores feeding should be done at minimum twice a day, feeding small amounts at a time as most Xanthichthys prefer to eat their food free flowing in the water column.
With the dietary needs of this fish, the frequent feedings will undoubtably lead to more dissolved organics in your system. Ample amounts of water flow should be utilized to keep detritus and uneaten food suspended, as well as a large protein skimmer and some form of nutrient export such as a macro-algae refugium. (As many of you know one of the benefits of a macro-algae/live rock refugium is an increased number of micro-crustaceans and zooplankton in your system, a natural food source for your Xanthichthys.)
Balistidaes in general are highly resistant and resilient animals when it comes to disease in comparison to other animals offered in the trade such as Chaetodons (Butterflyfish) and Acanthuridae (Surgeonfish/Tangs). If your Xanthichthys is displaying abnormal or 'sickly' behavior I would investigate environmental issues (water quality, aggression) prior to considering any disease. As all Xanthichthys are wild collected, they are susceptible to the common parasites and protozoan diseases commonly dealt with in marine aquaria. Any administration, treatment, with medication or antibiotics should never be done in a sterile quarantine tank and not the display to ensure proper dosage and avoid subjecting other denizens to unnecessary treatment.
Compatibility in the Home Aquarium
'Collateral Damage is your responsibility to, if you have a doubt don't pull the 'Trigger''
For keepers of reef and mixed invertebrate aquaria
this is likely the 'payoff' section of the article you've
been looking forward to. While I prefer to avoid using the term
'reef-safe' which I consider to be a gross generality and
misnomer, as technically by the hobby definition all fish are not reef
safe as they live there and therefore eat something on the reef;
Xanthichthys are certainly better candidates for inclusion in mixed
marine aquaria than other members of the Balistidae family. While
even large Xanthichthys should ignore most
sessile invertebrates completely, they are not above moving them and
rocks in their pursuit of other food and therefore can cause collateral
damage. Likewise while they often ignore small crustaceans and
echinoderms, these can overnight become appealing to a Xanthichthys
palette, especially X. ringens. Alternatively Xanthichthys are
often poor choices for large 'tough' fish only aquaria that
houses more aggressive Balistidaes and large, 'high speed'
predators/territorial 'war' mongers. Due to their more
cryptic behavior these fish can often be scared into submission,
permanent hiding, when housed with overtly aggressive individuals
leading to starvation if not outright shock and death through
'This is my Trigger, this is my fish, I hope it doesn't fight - I just want to have fun.'
If collected properly and housed in an adequate
habitat with appropriate tank-mates, Xanthichthys can be quite
personable, long lived (15 years at some reports) specimens. Just
don't let their more mellow disposition, they are still Triggers
and still have that ability to become monsters, albeit less than many
other members of the family. It's true that there are no
guarantees with animal behavior in this hobby, but many aquarists,
myself included have calculated that the Xanthichthys can be worth the
risk in their quest to create a stunning display.
Sources and/or extra
A REVISION OF THE TRIGGERFISH GENUS XANTHICHTHYS,
WITH DESCRIPTION OF A NEW SPECIES; John E. Randall, Keiichi Matsuura,
and Akira Zama (1978)
Balistes polylepis and Xanthichthys
caeruleolineatus, Two Large Triggerfishes (Tetraodontiformes:
Balistidae) from the Hawaiian Islands, with a Key to Hawaiian Species;
JOHN E. RANDALL AND BRUCE C. MUNDy
Michael, S.W. 1998. Reef Fishes Volume 1. Microcosm. Shelburne. pp. 624.
Michael, S.W. 1999. Marine Fishes: 500 + Essential-To-Know Aquarium Species. Microcosm. Shelburne. pp. 448.
Hydrodynamics of Balistiform swimming in the Picasso Triggerfish, Rhinecanthus aculeatus; Loofbourrow, Hale (2009)
Fungal diseases of fish, Roy P.E. Yanong, VMD (2003)