Fish Articles

Filefishes, Family Monacanthidae

In many ways just as appealing in color, pattern and behavior as their toothier cousins the triggerfishes, filefishes are more suitable tankmates on the basis of better-temperedness. Where any given trigger would rather "bite than flight", files would rather "high-fin" it off to hiding.

Given adherence to a few selection and maintenance criteria, the novice can experience success in keeping many members of this group of fishes.

Classification: Taxonomy, Relation With Other Groups

Nelson used to place the filefish in a subfamily, the Monacanthinae (= "one spine") sharing the family Balistidae with the triggerfishes, subfamily Balistinae. Note the convention in zoological nomenclature (scientific naming) of designating families with an -idae ending and subfamilies with -inae. Simple stuff, yes? But, no there are some kill-joy old and current timers (I'm one of them) who "elevate" the filefishes to their own family level, the Monacanthidae. No sweat.

These bad boyz find themselves in turn cataloged in the "most advanced" Order of living fishes, the Tetraodontiformes, along with such characters as the various puffer families.

Who Cares About This Scientific Naming Anyway?:

"News Flash": We break here for an important side note here concerning any and all references to these fancy scientific names, and higher classifications. I want to tell, maybe the word is show you the value in bringing up family, order, species et al. naming at all.

First, there is the matter of "common symbolism", that is, language itself. When you read or hear Yellow-tailed blue tang what comes to mind? Do you think this is the same for everybody who might read this book? It is indeed not.

As the "Aquatics Buyer" for the mass-merchandiser PetCo this point was made to me in trying to assign one "name" for every SKU (stock keeping unit number) that in turn referenced a given type of product (or livestock) for "inventory control". Our stores on the eastern seaboard would call me desperately seeking the "hippo tang" or "palette-surgeon" SKU. What we're these fishes? Yes, the same species Paracanthurus hepatus, by other common names. Unfortunately, the computer types in "MIS" (management information services) wouldn't help; "There's only so many SKU's available, and only so many characters/letters per SKU...". Ho-boy; I think this matter was resolved (not solved) by "fudging" the common name with an analog device (marking pen) on the livestock's label.

My second point in bringing up the value of scientific naming has to do with "higher" classifications like family-this, suborder-that. I figure that I'm like you and most everyone else; I have an interest in pet-fish and willingly dedicate some portion of my consciousness to their appreciation; but we also have many other items clogging up our "read-only-memories" (biological ROM's). The higher classification schemes of taxonomy help us to store information on a vast number of organisms in a more concise manner. For this family, the filefishes, you know that they're closely related to the triggers; and that both families are not too distant from the families of puffers. What does this all mean? Well, sure they have structural, possibly evolutionary kinship with one another; but more useful to us as aquarists, their close taxonomic affiliation has practical implications.

Files, triggers and puffers all get around by the same sort of undulation of their dorsal and anal fins; they eat about the same meaty foods in approximately equal proportions and intervals. Guess what? All of them suffer from similar maladies and infections, and are treatable in likewise fashion. Their environmental demands, reproduction, intelligence/behavior, the fact that they all will bite you... are also comparable. Memorizing and using this information for each individual animal would be hard compared with knowing it "by higher category". This is the practical value of "higher classification". Use it if you see worth in it personally, otherwise don't let it bother you.

Back to Classification of the Filefishes:

Filefishes themselves are identified by having usually two dorsal spines- the second may be small or absent. Their soft dorsal, anal and pectoral fin ray spines are unbranched. They have small scales not arranged in regular series. Their bodies are prickly to furry to the touch (hence the name natch). Upper jaw usually with six teeth in outer and four in the inner series.

About 31 genera including Aluterus (=Alutera), Amanses, Cantherhines, Chaetoderma, Monacanthus, Oxymonacanthus, Paraluteres, Pervagor, with about 95 species.

Species of Use/Disuse By Aquarists:

Acreichthys tomentosus (Linnaeus 1758), the Bristle-Tail Filefish, is the "Man of the Hour" if you have the ultimate Aiptasia/Glass Anemone woes... it is reputedly the predator par excellence of these noisome pests. Indo-West Pacific in distribution. To four inches maximum length. One in the Waikiki Aquarium, Oahu, Hawai'i.
Aluterus schoepfi (Walbaum 1792), the Orange Filefish. East and West coasts of tropical Atlantic and Gulf of Mexico. To two feet maximum length.
Aluterus scripta (Osbeck 1785), the Scrawled Filefish. Circumtropical. Sold in the trade occasionally, but gets way too big. Shown a tiny one foot specimen and a two foot youngster (Bunaken/Indonesia and Red Sea respectively) (to forty inches overall length).
Anamses scopas (Cuvier 1829), the Broom Filefish. Indo-Pacific including the Red Sea, where this picture was made. To eight inches overall length. A bit shy, even for the family.
Cantherhines dumerili (Hollard 1854), the Whitespotted Filefish. Indo-Pacific. To fifteen inches maximum. Feeds on a variety of invertebrates including corals as this specimen is doing in the Andaman Sea off of Thailand.
Cantherhines macrocerus (Hollard 1854), the Orange Filefish in the pet trade is called the American Whitespotted Filefish in the sciences... unfortunately, in part because it occurs on both coasts of the tropical Atlantic. One of the more common Filefish offerings in the world of aquariums. To twenty-six inches in length. Images of a six inch individual and one foot adult specimens in the Bahamas.
Cantherhines pullus (Ranzani 1842), the Orange-spotted Filefish. Tropical West Atlantic. To eight inches in length. A more common aquarium offering.
Cantheschenia grandisquamis Hutchins 1977, the Large-Scaled Leatherjacket. Western Pacific; Australia. To ten inches. A beauty for sure. This one off Heron Island.
Chaetodermis pencilligera (Cuvier 1816), the Prickly Leatherjacket. Indo-West Pacific. To twelve inches in length. This six inch specimen in an aquarium display.
Oxymonacanthus longirostris (Bloch & Schneider 1801), the Harlequin Filefish or Orange Spotted Filefish in the aquarium interest. The most commonly offered member of the family... and rarely alive for more than a week in captivity. In the wild almost only eats Acropora polyps.
Paraluteres prionurus (Bleeker 1851), the Blacksaddled Filefish. Indo-Pacific, but not the Red Sea. To four inches in length. A mimic of the Sharpnose Puffer, Canthigaster valentini. Aquarium and Maldives specimens.
Pervagor melanocephalus (Bleeker 1853), the Red-Tailed Filefish. Indo-West Pacific. To six inches in length. One of the best Files for captive use.
Pervagor spilosoma (Lay & Bennett 1839), the Fantail Filefish. Eastern Pacific, principally Hawai'i where it's occasionally shipped out of. To seven inches overall length. Feeds on algae and benthic invertebrates, including corals.
Scobinichthys granulatus (White 1790), the Rough Leatherjacket. Indo-West Pacific, Australia. To twelve inches in length. This one in the London Aquarium, U.K.

Natural Range

Filefishes occur in shallow reef and rocky areas in Atlantic, Indian and Pacific marine environments. Though often present, sometimes in large numbers, they are frequently missed by noisy, unobservant divers.

Size:

Most files reach around 15cm. (six inches to us old timers); one gets to a maximum length of one meter; Aluterus scriptus. Now that's a big file!

Selection: General to Specific

Healthy specimens are characterized by good color, without blotchy or necrotic patches, behavioural elements (curiousity, activity), and active feeding.

Most species make excellent captives, except unfortunately the often-offered long nosed or orange-spotted filefish (Oxymonacanthus longirostris). This one only eats coral polyps. Leave it in the ocean if you can't provide adequate care. In fact, I think the whole genus is corallivorous and should be avoided./p>

A few notes on filefish capture for the aqua-venturer. Commercially, small individuals are taken with hand nets at night or net-dragged out/over eel grass and such. Larger specimens are taken in mesh fish traps and barbless hook and line baited with some sort of tasty meat.

Environmental: Conditions

Habitat

Filefishes rely a great deal on subterfuge to avoid predation. Relatedly, they seem to prosper in physical surroundings that complement their gaudy integuments. Real or artificial decor schema that allow a blending/camouflaging of files makes them feel at home. Provide them homes where they can appear inconspicuous.

Chemical/Physical

Not picky. Natural water or no. Relatively insensitive to changes, high or low specific gravities, metabolite build-ups...

Display

Give them plenty of opportunities for hiding and wedging into caves and crevices like triggers.

Behavior: Territoriality

This whole Order is best characterized as very individualistic. In general, filefishes are docile toward members of the same species and their family members when small or necessarily temporarily crowded (at the Dealer's); but watch out! They can become overtly intolerant without any apparent provocation. Most are best kept one file to the tank.

Introduction/Acclimation

Placing of most filefish species and specimens is unceremonious. Quinn suggests his favorite "drip" method of blending "old" shipping water with "new" system water. I'll still plug my raw freshwater dip method to prevent/dilute pest, parasite and pollution introduction. (See next few Sections)

Monacanthinids are not touchy in terms of handling stress. They typically "brighten up" shortly after introduction, displaying curiousity about their new digs.

A caution concerning netting files; their skin and fins get stuck but good in most consumer nets. It's much better for all parties to do away with nets and "hand-lift" specimens or scoot them into a container underwater if/when they have to be moved.

Predator/Prey Relations

The group are opportunistic omnivores, bordering on tiger barb nippiness in saltwater equivalency. Keep your eye on them, though they usually cause little outright damage, being followed and chewed on continuously can get on one's nerves.

As for "turnabout is fair play", most wanna be predators find filefishes too tough to chomp. In addition to the height-increasing dorsal "trigger" mechanism, they share the triggerfish's capacity for slightly enlarging their bodies by expanding a ventral flap supported by a large movable pelvic bone.

Reproduction, Sexual Differentiation:

Some species have been observed spawning in the wild. Eggs are noted as green in color, about a millimeter in diameter, demersal (on the bottom), adhesive, hatching in a couple of days after sunset, becoming pelagic, planktonic larvae.

In some species, males are slightly larger and more colorful.

Locomotion:

Effected most of the time via undulations of the median fins. At times of need/desire, the tail comes into play for short, fast bursts of straight speed.

Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes

Most any and all frozen and fresh foods will sustain files. Meaty clams and crustacean foodstuffs will always shake one out of the doldrums. Don't neglect their need for vegetable material though.

Stomach contents analyses reveal a broad mix of hydrozoans, algae, sedentariate polychaetes, sponges, gastropods, amphipods, gorgonians, sea grass (a true vascular plant), colonial anemones and tunicates. Not good reef-tank candidates.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

Martin mentions the efficacy of using tetracycline HCL for treatment of "anomalous" bacterial anomalies, in his case presumed digestive infection manifest in non-feeding. He lists administering the antibiotic directly to the system water at 50 mg per gallon. Any medication advice from anywhere is to be followed in a seperate treatment tank, not your main system.

Filefishes are available seasonally and geographically. Don't let their shy, delicate appearance fool you, a few make interesting, affordable aquarium specimens.

Bibliography/Further Reading:

Barlow, G.W. 1987. Spawning, eggs and larvae of the longnose filefish Oxymonacanthus longirostris, a monogamous coralivore. Environ. Biol. Fish.; vol. 20, no. 3 183-194. 1987.

Eristiwady, T. & P. Geistdoerfer. 1991. Biological aspects of Monacanthus tomentosus (Monacanthidae) in the seagrass beds of Kotania Bay, West Seram, Moluccas, Indonesia. Mar. Biol.; vol. 109, no. 1, 135-139. 1991.

Hauser, Hillary. 1984. Skin Diver Magazine's Book of Fishes. The Photographic Book Company. 1984.

Martin, Robert A. 1976. Scrawled filefish. Marine Aquarist, 7:6, 1976.

Nelson, Joseph S. 1976. Fishes of the World. John Wiley & Sons, Inc.

Quinn, John R. 1990. Fooling around with filefish. T.F.H. 10/90.