The Copperband Butterflyfish, Chelmon rostratus, is one of the most distinctive saltwater fish available for the marine aquarium. Its laterally compressed, silvery-white body is crossed by bold copper-orange vertical bands, while a prominent false eyespot near the rear dorsal fin helps complete its unmistakable appearance. The species is also recognized by its exceptionally long, narrow snout, which is naturally adapted for extracting small invertebrates from cracks and crevices in reef structures. Adults reach approximately 8 inches (20 cm) in total length. Native to the Indo-West Pacific, the Copperband Butterflyfish occurs from the Andaman Sea through parts of Southeast Asia and the western Pacific to the Ryukyu Islands and Australia. It inhabits rocky shores, coral reefs, estuaries, sheltered bays, and silty inner reefs, generally at shallow depths to about 25 meters. In an established marine aquarium, Chelmon rostratus can become a spectacular centerpiece fish, but it requires considerably more attention than many common community species. Its specialized feeding behavior and tendency to acclimate slowly make specimen selection and consistent feeding particularly important. Although often maintained successfully in reef aquariums, it is best considered reef safe with caution because tubeworms, clams, small invertebrates, and occasionally corals may be investigated or consumed. Quick Care Guide Care Level: Expert OnlyMinimum Tank Size: 120 gallonsTemperament: PeacefulDiet: Carnivore / Benthic Invertebrate FeederReef Safe: With CautionRegion: Indo-West PacificScientific Name: Chelmon rostratus Although smaller minimum aquarium sizes are sometimes suggested, a 120-gallon or larger aquarium provides a more suitable long-term footprint for this deep-bodied, approximately 8-inch butterflyfish. Quality Marine specifically notes that while 75 gallons may represent a bare minimum, a 120-gallon aquarium with a wider footprint is preferable. Tank Requirements The Copperband Butterflyfish should be housed in a mature, well-established saltwater aquarium containing substantial live rock along with ample open swimming space. Rockwork should include caves, overhangs, crevices, and irregular surfaces that allow the fish to forage naturally throughout the day. This species spends considerable time inspecting rockwork for worms, crustaceans, and other small benthic prey. A biologically mature aquarium with abundant microfauna can therefore be particularly valuable during acclimation and between scheduled meals. Provide strong filtration, good oxygenation, stable water chemistry, and moderate water movement. The aquascape should be open enough to allow comfortable swimming while still offering plenty of sheltered areas where the fish can retreat when startled. No specialized substrate is required, although a mature reef-style aquarium with established rockwork generally provides the most natural environment. Avoid introducing this species into a newly established or biologically sterile system whenever possible. Diet and Feeding The Copperband Butterflyfish is primarily a carnivorous benthic feeder. In nature, its elongated snout allows it to extract worms and other small invertebrates from holes, crevices, and reef surfaces. Georgia Aquarium lists benthic invertebrates as its primary diet, while aquarium husbandry references emphasize its preference for small crustaceans, worms, and similar foods. In captivity, offer a varied selection of mysis shrimp, enriched brine shrimp, chopped clam or mussel, finely chopped shrimp, krill, copepods, frozen plankton blends, and other finely chopped marine seafood. Live foods may be useful for encouraging a newly introduced specimen to begin feeding. Copperbands frequently eat slowly and may be outcompeted by aggressive or fast-feeding tankmates. Several small feedings throughout the day are preferable, particularly during acclimation. Food can also be placed into rock crevices or feeding devices that allow the fish to use its elongated snout naturally. A specimen that refuses food should be taken seriously. This species can lose condition while continuing to pick at rockwork, so active feeding and body weight should be monitored closely. Some individuals consume Aiptasia anemones, which has made the species popular for natural pest control, but this behavior is not guaranteed and should never be the primary reason for purchasing the fish. Temperament and Tankmates The Copperband Butterflyfish is generally peaceful and somewhat shy toward unrelated marine aquarium fish. It is best maintained with peaceful to moderately assertive tankmates that will not harass it or prevent it from feeding. More aggressive fish can make acclimation especially difficult for this relatively deliberate feeder. Suitable tankmates can include peaceful tangs, gobies, blennies, cardinalfish, anthias, fairy wrasses, and other non-predatory community fish. Avoid highly aggressive triggers, large predatory wrasses, or territorial species likely to dominate feeding time. Copperband Butterflyfish can become territorial toward similar butterflyfish and closely related species. Keeping a single specimen is generally the simplest option. Wild fish occur both singly and in pairs, and compatible pairs may be maintained in sufficiently large aquariums, but two unrelated individuals should not automatically be expected to coexist peacefully. Reef Compatibility The Copperband Butterflyfish is best classified as reef safe with caution. Many specimens can be successfully maintained in coral-dominated reef aquariums without significant coral damage, but individual behavior varies. Feather dusters and other tubeworms are especially vulnerable, and the fish may also nip at clams and other small or sessile invertebrates. Some individuals may investigate fleshy corals as well. Ornamental shrimp and larger snails are often ignored, but very small crustaceans and other microfauna fall within the species' natural feeding strategy. A Copperband should therefore not be considered completely invertebrate-safe. Aquarists keeping valuable tubeworms, clams, or particularly fleshy corals should be prepared for the possibility of predation or persistent nipping. Water Parameters Temperature: 75–80°FSpecific Gravity: 1.024–1.026pH: 8.1–8.4Alkalinity: 8–12 dKH Maintain clean, highly oxygenated saltwater and prioritize stable conditions over constantly adjusting parameters to reach exact numbers. Sudden changes in salinity, temperature, or pH should be avoided, particularly during acclimation. Common Considerations Challenging feeder: Copperband Butterflyfish are considered difficult aquarium fish because newly introduced specimens may refuse prepared foods or eat too slowly to compete effectively. Mature aquarium strongly preferred: Established rockwork containing copepods, worms, and other microfauna provides valuable natural feeding opportunities. Reef safe with caution: Tubeworms, clams, small invertebrates, and occasionally fleshy corals may be eaten or damaged. Aiptasia control is not guaranteed: Some individuals readily consume Aiptasia, while others completely ignore it. Adult size and swimming room: Chelmon rostratus reaches approximately 8 inches and benefits from a wide, mature aquarium with substantial rockwork and open swimming space.
