The Raccoon Butterflyfishes: Chaetodon lunula and Chaetodon fasciatus

Author: Bob Fenner

A marine fishkeeping expert profiles two gorgeous and hardy butterflyfishes named for their raccoon-like markings.

My Favorite Butterflyfishes

What’s your favorite butterflyfish? A “Heni,” threadfin, a golden, a double saddle-back? At the top of my personal list are the two—yes, two—raccoon butterflies, Chaetodon lunula (“Key-toe-don lew-new-lah”) and Chaetodon fasciatus (“fah-see-ah-tus”).

These B/Fs (industry shorthand for butterflyfishes) are hardy, disease-resistant, ready eaters to the point of being porky, and strikingly beautiful. As marines go, they’re moderately inexpensive and readily available. Specimens that have been conscientiously collected, held, and transported are long-lived in captivity. Ones that have not will be easy for you to discern with the information offered here.

Classification: Taxonomy and Relation to Other Groups

The raccoons are just two of 88 species in the giant genus Chaetodon, of the butterflyfish family Chaetodontidae, which consists of 10 genera and some 120 nominal species.

Chaetodon lunula

Chaetodon lunula, “the” raccoon butterfly, is found widely throughout the tropical Indo-Pacific, eastward even to Hawaii (my favorite source), and westward to the Indian Ocean, but it is missing from the Red Sea. Though not as attractive as its namesake in the Red Sea, C. fasciatus, the Indo-Pacific raccoon is just as hardy, and it’s a very good choice for eating pest Aiptasia anemones in reef tanks, though it will consume coral polyps in some cases.

Red Sea Raccoon

The Red Sea raccoon butterfly is so named for its restricted distribution, found only in the Red Sea and the adjoining Gulf of Aden. Happily for the world of marine aquarists, Red Sea livestock is becoming much more available in terms of numbers to be had and lowered cost. C. fasciatus is a beauty that will eat all types of foods in captivity, including coral polyps. It grows to some 10 inches (25 cm) in length in the wild but only about half that in captivity.

Appearance

Both species bear black and white crescent bands over the face and eyes, imitating the raccoon-mask face of their terrestrial namesake. They’re similarly colored: yellow, black, and white on first glance, yet look closer. The Red Sea species lacks the Indo-Pacific’s caudal peduncle (the area right before the tail fin) black spot and the oblique yellow stripes behind the head. Note also the differences in the Red Sea species’ white masking (it has less of it); its bolder, more variegated body band markings; and its gorgeous red margining on the unpaired fins.

Size

Raccoons can reach more than 9 inches (23 cm) in total length and grow an inch (2.5 cm) or more in half a year. Not the biggest B/Fs, but close. They need room to swim and grow.

Selection: General to Specific

The following course of observation and action is important in selecting a healthy butterflyfish:

1. Timeliness: how long has the dealer had the fish? I strongly suggest holding off purchasing butterflies for a good week or two after arrival. Shaky individuals will have straightened out by then, or gone the route.

2. Feeding: any marine fish of considerable cost should have to pass the acid-test of whether it is eating. No feeding, no sale.

3. Appearance: being off-color and having any reddening of the mouth or fin bases should disqualify a prospective purchase. Most often because they have suffered mishandling, such specimens refuse food and rarely recuperate.

4. Size on acquisition: small and large butterflies ship and adapt poorly; avoid those under 3 inches (7.5 cm) and over 5 inches (12.5 cm) if at all possible. Intermediate-size specimens acclimate well to captive conditions.

Collecting Your Own

It’s possible to collect butterflyfishes on your own if you just happen to be in the area. The raccoons and all other butterflyfishes are captured using a “fence net” arranged as a barrier, and hand nets (and possibly poles) to drive intended specimens against it.

Environmental Conditions

Habitat

Raccoon B/Fs live in shallow regions of coral reefs with both ready holes to swim in/out and dive into, and plenty of open space. Note that these species can and do get pretty big (more than hand size) and don’t tolerate crowding; a small specimen requires a good 15 gallons (57 liters) itself, a larger individual a minimum of thirty gallons (114 liters).

Chemical/Physical

Butterflyfishes as a whole do not appreciate much in the way of nitrite or nitrates. A successful approach to their keeping is to place them into established (six months plus) aquariums that are adequately equipped with filtration geared toward maintaining low organic concentrations (e.g., foam fractionation, chemical absorbers).

Steady and high specific gravity (1.025 for both species), and pH (ideally 8.3) are requisite. Bottom line: these fishes need consistent high-quality water.

Filtration

A “dream” filter setup might involve a separate “refugium” aquarium to circulate water to and from your main display system. This other tank would have its own lighting gear and be filled chock-a-block with thriving live rock, a live sand arrangement to eliminate nitrates, heating, and a protein skimmer. It would even provide some supplemental live food!

Behavior

Territoriality

Raccoon butterflies are most often seen singly, periodically in pairs, only occasionally in groups. Unless you purchase or capture them together, though, they are best kept one to a tank. Likewise, other butterflyfish family members can butt heads should they be closely matched size-wise or if the system is crowded. My suggestion is to keep an inch or so difference in your new chaetodonts and introduce the smallest first, with a span of a few weeks between them.

Introduction and Acclimation

Following a two-week quarantine (or at least a brief freshwater dip), even coming from a reputable dealer, a mixing or dripping of waters acclimation procedure should be followed, placing the new specimen in its new home under low illumination for a day. Do this when you have time to observe carefully. The first minutes to an hour are critical in terms of determining whether or not the raccoon will take or be accepted by its tankmates. Watch your livestock.

Predator/Prey Relations

I’ve heard of small Chaetodon lunula kept in reef setups, but I don’t advise it; raccoons will pick at coral and sample other soft-bodied invertebrates to pieces. Raccoons are good community fishes for fish-only systems. Other fish species leave them alone, unless they’re bite-size, and they are generally “live and let live” in attitude, with the possible exception of members of their own kind and butterflies of similar size and shape.

Reproduction, Sexual Differentiation/Growing Your Own

Butterflyfishes are egg-scatterers, releasing their gametes to the whims of surface currents cued by moon and tides. Larval young develop through a strange armored “tholichthys” stage as pelagic plankton, settling down (hopefully) as miniature adults. Like most other chaetodonts, the raccoon species are indistinguishable sexually. All specimens offered for sale are wild-caught.

Feeding: Types, Frequency, Amount, Wastes

As mentioned previously, both raccoon species are enthusiastic eaters. Once they have been trained to accept non-living foods you will have to literally “beat them with a stick” to keep them from feeding. New arrivals may require live offerings initially; brine shrimp and tubifex work well, as does an opened fresh clam. In the wild raccoon B/Fs feed primarily at night, so initially offering food toward the evening is worth considering.

I have seen these fishes maintained on little more than dry-prepared foodstuffs, but with consequent loss of color and vitality. Do alternate meaty foods into their diets (shrimp, clam, mussel, frozen insect larvae, etc.) on a regular and frequent basis. B/Fs are browsers that become bored and skinny when fed only once a day; feed often in small amounts.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

Except when exposed to new livestock that has brought in bugs with it, these fishes are historically clean. If yours look punkish and are refusing food, look first and foremost to diminished water quality and second to bullying by a tankmate. Be cautious as to unnecessarily treating these fishes (and your other marine livestock) with medications. The dreaded saltwater ich (Cryptocaryon) may be cured via standard copper treatment, but it is best to avoid it entirely through quarantine and/or dipping.

Add a Raccoon

The raccoon butterflyfishes are two of the best of the family. As omnivorous feeders on sedentary invertebrates and plankton, they easily adapt to aquarium fare. For chaetodonts, they’re parasite-resistant. What’s more, both are beautiful and interesting behaviorally. If you have an uncrowded, spacious system that is well established and filtered, do consider an aquatic raccoon.