Copperbanded Butterflyfish

The beautiful copperband butterfly is a fishkeeping challenge.

Q. I am a relatively new marine aquarium keeper. I have had a 75-gallon tank for about 13 months that contains several small damsels and a pair of false percula clowns. The tank contains about 60 pounds of live rock with some soft corals and a sebae anemone for the clownfish. I am ready to try a more demanding fish.
I really like the copperband butterflyfish, but some people tell me they are impossible to keep. However, a local storeowner said you can keep them. I have also been told that it will eat coral and anemones. There is a similar butterflyfish that I have been told is hardier. Is this true? 
— Steve Nichols

A. I agree that the copperband butterflyfish (Chelmon rostratus) is a true beauty – and yes, there are differing opinions on whether you can successfully keep them. This is due, in part, to the fact that individual copperbanded butterflyfish vary in hardiness. Some settle into their new homes within several days, and begin eating fresh and frozen foods, while many refuse to feed.

Why the big difference? Some of it is related to how the fish is captured and handled before it gets to your tank. For example, individuals collected from Australia tend to do better in captivity than those exported from the Philippines, reflecting differences in collecting and holding practices. Be prepared to pay more for Australian C. rostratus, but it is well worth paying more for a fish that is likely to be more healthy. It has been suggested that brightly colored individuals from Asia have been collected with cyanide and are more likely to meet an early demise, but I am not aware that this has been scientifically confirmed.

To increase your chances of success with a copperband butterfly, select your fish very carefully. Avoid emaciated individuals; thin specimens are not likely to recover. Some aquarists have suggested that smaller individuals (around 3 inches in length) fare better in captivity than adults. The idea is that smaller individuals are more likely to acclimate to a new food source than an older fish. Be aware that the metabolic needs of a juvenile fish will be higher than that of an adult. As a result, you will need to make sure you feed a young fish frequently or ensure there is an adequate natural food source in the aquarium. Copperband butterflyfishes are thought to feed heavily on tubeworm feeding appendages and small crustaceans. A tank with live rock (like yours) will provide some normal fodder. This will provide a hungry copperband with nutritional snacks between meals. Natural prey items are also important if a newly added C. rostratus is reluctant to eat aquarium foods when first introduced to the tank.

Some C. rostratus will require live foods to induce a feeding response. Foods such as live clams or black mussels that have had their shells broken open, or sessile invertebrate-encrusted live rock can initiate feeding. Live brine and frozen mysid shrimps have also been used to get reluctant fish to feed. You may be able to induce a finicky copperband to feed if you add another butterflyfish that will readily accept captive fare (e.g., the yellow longnose butterflyfish, Forcipiger flavissimus). By watching the other butterflyfish, the C. rostratus may begin to mimic it and start to feed. This is known as social learning. Of course, other butterflyfish species may be more of a threat to ornamental invertebrates than a copperband and may compete with it for the natural fodder on the live rocks.

A copperband will often behave aggressively toward members of its species. When they fight, they ram their heads together and push against each other. It is prudent to keep only one C. rostratus per tank (especially in a tank as small as yours). If you have a very large tank, it is possible to keep a male-female pair – however, the sexes are difficult to distinguish. This fish may exhibit aggression toward other members of the genus Chelmon, but will usually ignore and is typically ignored by other butterflyfishes.

Most individuals (and other members of the genus Chelmon) can be kept in a reef tank with most soft corals and small-polyped stony corals – although some individuals may nip at large-polyped stony corals, certain soft corals (including xeniids and clavulariids) and zoanthids. One advantage in keeping a copperband butterflyfish in a reef tank is that most will eat glass anemones (Aiptasia spp.); however, some individuals will ignore them. One possible drawback to housing this fish in a reef tank is that it will decimate polychaete worm populations.

This species reaches a maximum length of about 8 inches in the wild. It may not get this big in captivity. While a 75-gallon tank could hold an adult C. rostratus, a larger aquarium would be preferable.

The copperband is very similar to the margined coralfish (Chelmon marginalis). In fact, juveniles of the two species are almost indistinguishable (young C. rostratus have a wider midbody bar). As C. marginalis matures, it loses the black eye-spot at the base of the dorsal fin, which differentiates it from adult C. rostratus. It is highly likely that the two species hybridize where they co-occur (Gulf of Carpenteria, northern Australia). Roger Steene, an expert on Australian butterflyfishes, has suggested to me that he thinks that C. marginalis and C. rostratus are probably the same species, just different color forms. It is generally considered that C. marginalis is more hardy than its close relative.

Another member of the genus is more durable than both of these species. It is MŸller’s butterflyfish (Chelmon mülleri). This species is limited in distribution to northwestern and Queensland Australia. Rather than living on clear coral reefs, it tends to occur in estuaries or around rocky islands. It is not as colorful as its genus members, but it is the best member of the genus for the home aquarium. It ships well, acclimates quickly if placed in a well-maintained aquarium and readily accepts a wide range of fish foods. In other ways, its husbandry is similar to C. rostratus (e.g., keep one per tank).

There you have it. The copperband butterflyfish is a challenging fish to keep. I suggest that most aquarists consider the equally as interesting, but much more durable, yellow longnose (F. flavissimus) or Müller’s for their aquariums. But if you are ready to accept the challenge (and follow the suggestions given here), and you obtain a healthy fish to begin with, it is possible to keep a C. rostratus for well over 10 years. Happy fish-watching!

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Fish · Saltwater Fish