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Related FAQs: Double Saddleback Butterflyfishes, Butterflyfish Identification, Butterflyfish Foods/Feeding/NutritionButterflyfish Compatibility, Butterflyfish Behavior, Butterflyfish Systems, Butterflyfish Selection, Butterflyfish Disease, Butterflyfish Reproduction,

Related Articles: The Genus Chaetodon

/The Conscientious Marine Aquarist

The Double-Saddleback

Bob Fenner

A Chaetodon ulietensis in Fiji

Butterflyfishes for  Marine Aquariums
Diversity, Selection & Care
New eBook on Amazon: Available here
New Print Book on Create Space: Available here

by Robert (Bob) Fenner

Butterflyfishes as a group are amongst the most conspicuous of tropical reef fishes, many being brightly colored and boldly patterned. Add to this their active flitting behavior and it's easy to understand their popularity with marine aquarists. Unfortunately, of the hundred plus described species, only a dozen or so Butterflyfishes make good aquarium charges. The Pacific saddle back Butterflyfish is a great aquarium choice.

Very often called and sold as the 'falcula' Butterflyfish, Chaetodon falcula ("key-toe-dahn" "fowl-cue-lah"), a similar, but separate species, the Pacific double saddle butterfly fish, Chaetodon ulietensis ("key-toe-dahn" "you-lee-ay-ten-sis") is an exemplary aquarium choice for several good reasons.

It is indeed a shame that this Western Pacific beauty is not imported more frequently. It is a voracious feeder on all foods, attaining a reasonable maximum length of about six inches. Chaetodon ulietensis ships well, adapts readily to captivity and is at the very resistant end of the spectrum in terms of disease susceptibility.

Classification: Taxonomy, Relation With Other Groups

Butterflyfishes, Family Chaetodontidae (Key-toe-dahn-tih-dee) are closely related to the Marine angelfishes, Family Pomacanthidae; according to older accounts they are subfamilies of a larger grouping. There are some one hundred twenty legitimate species of chaetodonts, ninety percent are Indo-Pacific, a dozen hail from the tropical reaches of the Atlantic Ocean.

Butterflyfishes are characterized as having palm shaped, flattened bodies sporting elongated snouts with prising teeth; hence the meaning for the family name Chaetodont, "bristle-teeth".

The similar appearing relative to the Pacific double-saddle B/F (a notation used "in the trade" for Butterflyfish that we'll adopt here) is the 'true' falcula, or less confusingly called Indian Ocean double-saddle B/F. The two species are easily distinguished on the basis of color and markings:

1) Pacific Double-Saddle B/F, Chaetodon ulietensis

2) Indian Ocean Double-Saddle B/F, Chaetodon falcula

Item: Shape and extent of saddle markings:

1) Bar-like, more than half the girth.

2) Wedge-shaped, less than half the girth.

Item: Black dot on caudal peduncle:

1) Black dot with yellow above and below.

2) Completely black band with no yellow.

Item: Extent of yellow body color:

1) Color starts abruptly behind rear saddle

2) Bright yellow on dorsal surface as well as rear.

Want more? See Borsom in the references for more notes on the similar appearing true falcula B/F. 

Natural Range: 

The Pacific double saddle B/F is common in the western Indo-Pacific. It can be found in good numbers in Australia, new Guinea, the French Polynesian and Fiji Islands. This B/F is found in shallow coral reefs, at the surface to more than ten meters; especially in channels with brisk currents.

The species is named for it's type locality, Ulietea, where the specimen originally described by Cuvier in 1831 was collected.

Selection: General to Specific

Collecting Your Own 

A dream trip, but once you're there easily done with a barrier mist net plus suitable hand nets for snatching your catch once you've driven them in.

If you're a working class type who has to work so hard just to support your pet-fish habit, an individual B/F or two can be gotten from the usual sources. What to look for? Mainly a lack of the following:

Swollen, reddened areas around the mouth. 

Almost always a sign of sure doom from non-feeding & infection. Happens easily due to improper handling and shipping... and further, there is no excuse for it. The species in question ships like a dream; and bunk specimens should be returned to the sea, not forwarded.

Swollen, reddened areas anywhere else. 

Check the fish's body out thoroughly. No raised scales? Check out the fin ray origins.

Rapid breathing, in particular without complete closure of the gill covers. 

Evidence of heavy parasite load, chemical poisoning, collection, etc. trauma? Who knows? Who cares? Forget it.

Environmental: Conditions


 Large, open spaces with swift water movement; lots of stony coral rock and skeletons present.


Clean, high gas saturated water with almost complete absence of organics. Read this as good filtration, maintenance and water changes.


A brief mention of "fright and night" time coloration differences. B/Fs bleach out and basically 'decolorize' at bedtime and when spooked. Yes, you can literally poke around the reefs' at night and pick-up Butterflyfishes, among others sans nets. They can be found lying on the bottom, loosely lying between and betwixt coral and rock crevices. Therefore, if your B/F's look blanched out in the morning, don't panic. If it's during the day, better check out the cause, and as you know, "If and when in doubt, do a big water change". Thanks.


Good water quality only need apply. High pH's (low eights), no measurable nitrogenous metabolic wastes...


The bigger the system, the better, with some three dimensional structure to provide a sense of security and 'sleeping' space.

Behavior:  Territoriality

Some Butterflyfishes quarrel with members of their own kind and even other B/F species, especially at dusk and dawn. This latter fighting is thought to be driven by competition for 'sleeping' spaces. As Butterflyfishes go C. ulietensis is an exceptionally peaceful species amongst itself and other fishes. A pertinent "reason" may be that the double saddle back is a wide ranger in the wild, covering hundreds of square meters of reef space. Other species that hang out as singles or pairs in smaller lek territories tend to be more agonistic.


No new tanks! As a general rule this is so with all members of the family. They do not do well in unseasoned systems. Wait till the tank has been going a few to several months before trying them. As a seemingly direct anomaly to the previous, do be religious concerning regular partial water changes. B/F's really appreciate good, consistent water quality and for all practical purposes the best way the average aquarist can achieve this is frequent (weekly, every few week) partial (one quarter, fifth) water changes.

Acclimation of saddle-backs is no real problem. Butterflyfishes are very infrequently hassled as newcomers. Provide low illumination the first couple nights and be aware that the specimen(s) are feeding.

Predator/Prey Relations

As with all Butterflyfishes I'm familiar with, Chaetodon ulietensis is not a predator on other aquarium fishes, nor prey to any but the most belligerent bully (trigger, puffer, angel). Their overall philosophy may be summed up as live and let live.

Reproduction, Sexual Differentiation/Growing Your Own:

Angels and Butterflyfishes are broadcast spawners. Both have tiny, buoyant eggs that float at the surface for one or two days before hatching; resulting into strange critters called 'Tholichthys' larvae that are covered with bony plates. These fry go through a planktonic phase for a few weeks to months.

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

The various species of Butterflyfishes can be classified into five feeding types:

1) Hard (stony) Coral Feeders: such as C. trifasciatus and C. ornatissimus. Avoid these at all costs, they don't live in captivity.

2) Mainly Soft Corals with Some Stony Coral Eaters: e.g. C. unimaculatus, C. lineolatus. Don't try these either.

3) Small Benthic Invertebrate (worms, crustacea) Eaters such as those perennial favorites C. auriga & C. rostratus.

4) Zooplankton Feeders: Hemitaurichthys zoster and Heniochus species. Now you're getting warmer.

5) Opportunistic Omnivores that eat most anything. Like me and the Double back Pacific B/F. They accept all the above foods and algae.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

B/Fs including our star species here fall into one of two categories: Those that are great, strong specimens that you have to outright kill out of ignorance, and 2) Those that are unsalvageable no matter what you do and/or don't do. Your job, really, is to distinguish amongst those from the first and second group, then to pick out a healthy individual.

After the requisite dip/quarantine, bouts with protozoan parasites are easily cured with copper-based remedies and/or specific gravity manipulation.


Hey you pet-fish type, what are you looking for in potential marine aquaria specimens? Beauty, brains, staying power? This species has all that and much more. Have a big system? Consider a trio of the Pacific saddle back. They are gorgeous and tough, non-fussy eaters, and if your water quality is up to snuff, will provide you with many years of happy husbandry. 

Hey you pet-fish type, what are you looking for in potential marine aquaria specimens? Beauty, brains, staying power? This species has all that and much more. Have a big system? Consider a trio of the Pacific saddle back. They are gorgeous and tough, non-fussy eaters, and if your water quality is up to snuff, will provide you with many years of happy husbandry.

Bibliography/Further Reading:

Allen, Gerald A. & Roger C. Steene. 1978. Butterfly and Angelfishes of the World. Vol. 1 & 2. Aquarium Systems.

Axelrod, H.R., Burgess, W.A. & Raymond Hunziker. 1990. Atlas of Aquarium Fishes Reference Book. T.F.H. Publications, Neptune City, NJ.

Borsom, Michael E. 1978. Experiences with Butterflyfishes Pt. II. FAMA 11/78.

Burgess, Warren E. 1978. Butterflyfishes of the World, A Monograph of the Family Chaetodontidae. T.F.H. Publ. Inc.

Campbell, Douglas, 1980. Butterflyfishes, Pt. Two. FAMA 11/80.

Chlupaty, Peter. 1987. Burgess's Butterflyfish. TFH 4/87.

Fenner, Bob. 1990. Bannerfish butterflies, the genus Heniochus. FAMA 6/90.

Hunziker, Ray. 1992. The Ten Best Butterflyfishes. T.F.H. 6/92.

Moenich, David R. 1991. The Butterflyfishes. AFM 1/91.

Butterflyfishes for  Marine Aquariums
Diversity, Selection & Care
New eBook on Amazon: Available here
New Print Book on Create Space: Available here

by Robert (Bob) Fenner
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