Buyer Beware: The Copperband Butterflyfish (Chelmon rostratus)

Author: Tristan Lougher

Copperband butterflyfish are all too often doomed in aquariums, but it doesn’t have to be that way. Choosing a healthy specimen from the start, feeding properly, and creating the right environment are all essential for success with this species.

Advice for Selecting Marine Fish

Selecting marine fish for a new aquarium is a process that should begin long before entering your local aquarium store. Although advice from people who work with various fish species on a daily basis is often invaluable in helping compile a fish wish list, the selection process should begin with research and study to determine animals that will be compatible with each other and not outgrow your aquarium.

Depending upon the system, you might want to know what threat a particular species might present to corals or other sessile invertebrates or whether one species you were planning to keep is likely to leap from uncovered aquaria.

Often aquarists build their stocking list for fish around one particular species, the “must have” fish for which the aquarist sees no substitute. For many hobbyists, that species is the beautiful-yet-enigmatic copperband butterflyfish (Chelmon rostratus)—one of the most instantly recognizable, desirable, affordable, available, and wonderful fish that one could have the pleasure to own. Unfortunately, many aquarists stock individuals of this species without giving enough thought to their aquarium demands and many will not survive beyond a month or so. That said, the key to success lies not only in providing for a purchased specimen, but also in selecting the right individual initially.

Biology and Distribution

This widespread species of butterflyfish has a distribution that includes many of the major collection sites for fish intended for the marine aquarium hobby, including Indonesia, the Philippines, and Australia. A widespread and flexible species in its natural range, it is encountered in a variety of habitats, including the relatively murky waters found in river estuaries as well as more familiar reef environments.

In common with other fish species with elongated snouts and small, rather delicate-appearing mouths, it specializes in the removal of small invertebrates from cracks, holes, and crevices. In an aquarium environment, this includes tubeworms and, in some individuals, nuisance Aiptasia spp. anemones. That is the reason many aquarists stock this species.

The Problems

Although the various problems I will mention may not apply to every specimen of C. rostratus that arrives in the hobby, there are general issues that affect many individuals. Understanding some of these can help aquarists avoid poor specimens with little chance of survival or increase their chances of success with this species.


Fish collected from places far from their ultimate destination in the US or Europe must be able to endure the rigors of collection, transportation, and repeated acclimation. This process consists of withholding food to prevent the transport water being fouled, unpacking and acclimation at the wholesaler’s, transfer to retail shops, then purchase by customers, who stock them in their aquariums, possibly by way of quarantine systems. Many fish will recover from this ordeal in a relatively short time with no special intervention from the aquarist. However, for some species, the copperband included, action may be required.


The laterally compressed copperbands do not carry much in the way of excess muscle or fat, and the time from collection to arrival in a dealer’s or hobbyist’s aquarium can be rather significant. Thus the condition of many individuals is poor. If stocked into a reef aquarium where the emphasis might be on nutrient control and minimal feeding of fish, then further weight loss is likely to occur. Then factor in the occasional “welcoming committee” in the form of territorial tangs or other fishes that will harass the copperband, and we can begin to see why many individuals do not last long in the home aquarium.

Indeed, this is one of the best-case scenarios; the Internet is littered with examples of aquarists acquiring specimens that refuse to feed altogether. There seems to be a general consensus that copperbands are problematic to feed and it just goes with the territory. However, it would seem to be common sense that if you have the choice between a feeding or non-feeding specimen, you would opt for the former. So why not ensure that it is feeding before you buy?

Looking for Clues

Imports of the copperband from Australian suppliers are occasionally available and might be sold as “giant” or “Australian” copperbands—not to be confused with the Australian endemic Chelmon muelleri—another fish going by the name of Australian copperband. Although for various reasons, including increased overheads, fish from Australia may command a premium, copperbands from Australian sources tend to do rather better than those collected from other regions. Looking into the reasons these specimens tend to thrive better than their counterparts from other regions might give us ideas how success with all copperbands, regardless of their provenance, might be achieved.


“Giant” Australian copperbands are no larger when fully grown than those collected from Indonesia or the Philippines, but the specimens sold are closer to the maximum size for the species, which is around 8 inches in length. The principle behind this is, larger fish lose weight more slowly than smaller individuals and are, therefore, more resistant to starvation.

Consider that there is a general rule of thumb for marine fish that the largest and smallest individuals of a species are best avoided and intermediate specimens make the best additions to marine aquaria. The copperband appears to flaunt this to an extent in that Australian specimens are nearly fully grown, but a great deal of success can be had with intermediate-sized individuals from other parts of the Indo-Pacific if they’re given proper care and attention. However the smallest individuals, measuring only an inch or two, are certainly best avoided.

Pre-Shipping Rest

The aforementioned potential journey of a copperband is arduous, especially if the fish is dealing with the stresses of collection and shipping whilst simultaneously enduring a period of starvation. Although purging fish prior to shipping is a very necessary practice, they can still be rested between collection and purging and foodstuffs can be offered in this intermediate period. This provides valuable time for the fish to recuperate and get stronger so they’re better able to deal with the transport process and, therefore, recover more rapidly once acclimated at their shipping destination.

The balance between the need for purging and allowing fish time to recover from collection and, ideally, feed is a delicate one, but the best exporters will manage this. However, not all aquarists can source or afford Australian copperbands. In addition, the larger size of specimens means that they should be stocked in aquaria of 130 gallons or more, whereas smaller individuals from other sources can be added to systems of half this size.

So, what should aquarists look for when selecting specimens from Indonesia or the Philippines? It should be noted that copperbands from these sources are usually able to recover their pre-collection body weight if provided suitable rations. Issues occur primarily with non-feeding specimens or with individuals given insufficient food. In my experience, although non-feeding specimens will be present among them, it is their treatment after importation and acclimation that determines the success rate with copperbands. Fortunately, there are ways to avoid problems with copperbands regardless of their provenance. There are also practices that will help prevent any issues when they are actually in residence in the home aquarium.

Steps to Success

1. Research and Planning

Most problems with copperbands can be avoided prior to purchase. First, determine whether the fish you already have in residence will be compatible and consider potential future livestock purchases. Planning your livestock, mapping out the order in which they should be stocked, and adhering to the stocking regime can help avoid conflict. This is a good idea for any species but particularly the copperband, which should be added before aggressive fish such as tangs and angelfish. Consider any dietary necessities for the copperband, such as the regular addition of mysids or similarly rich foodstuffs, and determine whether any future additions might compete significantly for this.

2. Observation of Potential Specimens

If there is one process that can mean the difference between success and failure with the copperband, it is observation of specimens in dealers’ aquaria before purchase. It can help to have a look at a number of individuals over a number of weeks before committing to buy. First, check the body shape. Is it looking thin? Look at it head on, and pay particular attention to the area just above the eyes. Does it seem pinched or thinner than the head itself? Then check the flanks. Copperbands that have lost significant weight show a definite bulge in each flank—the location of certain internal organs and the swim-bladder—whereas specimens with good, acceptable body weight have smoother sides to the body.

Those fish that appear to be in good condition should then be offered food. Settled specimens should feed readily and with enthusiasm. The best copperbands will be swimming at the front of the aquarium facing out and expecting food.

Copperbands, like many butterflyfish, can experience an outbreak of the viral infection lymphocystis, manifested in cauliflower-like growths on the edges of the fins and occasionally the body. While these are not anything to worry about in terms of being contagious, they should be left alone until they clear up, usually a week or so later. Checking the fins of any marine fish for signs of pathogens should be a matter of course for all aquarists, although it is still worthy of mention that those of the copperband should be clear with no exposed fin rays in the dorsal fin.

After Stocking

Even in the best-planned, most thoroughly researched additions of the copperband, things can go wrong. When water quality or other conditions are less than acceptable (and not necessarily through measurable parameters, such as pH or ammonia levels), it’s not uncommon for an apparently vigorous specimen to stop feeding entirely. I am aware of several instances in which a specimen that had been feeding in a dealer’s aquarium refused food when placed in an aquarist’s system but then resumed feeding a couple hours after being returned to the dealer.

Although exact reasons for such phenomena may be difficult to ascertain, an awareness of this potential situation may help the frustrated aquarist make a decision regarding the future of the fish. Dealers will not appreciate the return of an emaciated specimen if all attempts to encourage it to feed have proved futile. Give it a couple days to settle, and observe it during feeding times. Might there be a reason it isn’t feeding, such as harassment from other fish? Is it picking at an abundance of naturally occurring food in the aquarium? Sometimes adding a morsel of food that will hang around for a little while, allowing the copperband time to discover it away from the frenetic activity of feeding time, is useful. Bivalve mollusks—clams, cockles, or mussels—are very useful in this role.

If an individual fish refuses to feed after a few days, then it is best to return it to the dealer. This assumes that you verified it was feeding before purchase. Chances are, returning it will give it a better chance of survival as there is a strong possibility it will feed again when stocked in the original or a similar aquarium.

But what should you do if you end up with a non-feeding specimen but have no information on whether it was feeding or not?

Tempting a Non-Feeder

Many aquarists will employ a quarantine aquarium before stocking any species of fish into their final home. Such a system is particularly useful for non-feeding copperbands, especially when stocked with plenty of live rock and an ultraviolet sterilizer installed to assist in the reduction of pathogens. Although the live rock precludes the use of copper-based parasite treatments, it does give individuals natural live foods to nibble at.

Getting the fish to feed on anything is a good starting point, and from there the aquarist can try other offerings. These can be live items, such as mysids, brine shrimp, and/or clams. Even living freshwater insect larvae, such as bloodworms or glassworms, may be readily accepted. Once a vigorous feeding response has been achieved using live offerings, then the aquarist can attempt a gradual weaning of the fish onto frozen offerings.

“Overfeeding” Newly Introduced Specimens

As previously mentioned, there is a tendency, particularly among reefkeepers, towards feeding fish just enough to keep them in good condition so that dissolved nutrients, such as nitrate and phosphate, stay within acceptable levels. This can work well even for aquaria containing a copperband butterflyfish. However, if an already-skinny specimen is introduced, even if it’s feeding heartily, the provision of meager rations is unlikely to reverse the weight loss.

Consider also the relatively strong water currents in reef aquaria in comparison to most dealers’ aquaria. Those strong currents mean the fish must burn more energy to hold its position in the aquarium. Even healthy specimens with good body weight are likely to lose condition over time.

Feeding Little and Often

Although skinny individuals should ideally be ignored as potential purchases, if one arrives in your aquarium, it may require small feedings several times per day if it is to thrive. Little and often is the key. Also, be sure to actually watch the fish feed, as in a busy aquarium, it may be outcompeted by its tankmates. Fine tune the ration as required, perhaps reducing it slightly as the fish recovers its condition.


Quarantine, or isolation, aquaria can be very useful in reversing the weight loss experienced by copperbands when they are recovering from the shipping process. Having a system in which several small feedings can be made in a day without worrying about the nutrient impact on other aquarium animals is extremely helpful. It is not impossible to do this where other fish and invertebrates are present, but it will usually necessitate the addition of significantly larger quantities of food.

Specimens That Won’t Feed

Unfortunately, there will always be individuals that, for one reason or another, will not feed. These reasons, if known, might be beyond the scope of the aquarist to fulfill, or they may remain a mystery. Butterflyfish in general appreciate highly oxygenated, clean water (with a relatively high redox value), but there are instances in which a copperband given apparently perfect conditions will not appreciate them. It’s best to return such specimens sooner rather than later.

Prep Before Purchase

The copperband butterflyfish is unlikely to lose its popularity with aquarists anytime soon. Provided it remains as inexpensive and available as it is currently is, it will always attract hobbyists willing to give it a home. I hope this article will help reduce the incidence of spontaneous, compulsive buys. A little time spent researching, planning, and observing a potential addition can save time, money, and not a little guilt and regret. Selectivity on the part of aquarists can lead to increased standards further up the supply chain, and that can only be a good thing.

The fact remains that a well-settled copperband is a truly magnificent fish that can provide many years of enjoyment for aquarists. One day, all specimens might have the reputation for hardiness that is currently held by those Australian individuals.