An elegant, copper-striped butterflyfish with a long tweezer-like snout, prized both for its beauty and its reputation as an Aiptasia-eater. It is notoriously difficult to feed in captivity and demands a mature, well-stocked reef and an experienced keeper.
ℹ️
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Indo-West Pacific, from the eastern Indian Ocean to the western Pacific
Climate
🌴 Tropical
Water type
🌊 Marine
Family
Chaetodontidae
Genus
Chelmon
Part of the Butterflyfish
Disc-shaped, ornately patterned reef fish admired for their elegance; many are specialist feeders demanding mature systems and careful diets, and most are not fully reef-safe.
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Photo coming soon
Minimum
Mature display reef
90 gal / 341 L mature reef
Chelmon rostratus is delicate and specialised. 90-gal minimum mature reef with abundant aiptasia / live rock, pristine water, and stable parameters. Difficult to acclimate — established system is critical.
Photo coming soon
Recommended
Reef-cautious display
125 gal / 473 L reef-cautious
125-gal reef-cautious display (may nip clams, feather dusters, LPS) with established live rock, varied prey items, and peaceful community. Patience required — they often refuse food initially.
Photo coming soon
Ideal
Large mature reef
180 gal+ / 681 L+ mature reef
Large mature 180-gal+ reef with deep aquascape, abundant live food (pods, aiptasia), and varied frozen options. Best survival rate by far.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Photo coming soon
Egg
Fish eggs are small, translucent spheres, often laid in clutches on plants, substrate, or in a nest — or carried/brooded by a parent in livebearing and mouth-brooding species. A dark eye spot and the curled embryo become visible inside as development progresses.
Photo coming soon
Fry
Newly hatched fry are tiny and semi-transparent, frequently still carrying a yolk sac that fuels them before they feed freely. They lack full fin structure and adult coloration, staying near cover until they can swim and forage on their own.
Photo coming soon
Juvenile
Juveniles look like miniature adults but with developing fins and muted or different markings; many species shift pattern and color as they mature. Growth is rapid at this stage given clean water and steady feeding.
Adult
Adults show the species' full size, finnage, and mature coloration, and are sexually mature. Many fish develop sex-specific differences in size, color, or fin shape, which can intensify during breeding.
Habitat & enclosure
House singly in a mature reef or fish-only system of at least 285 L (75 gal); larger is better for long-term success. Keep tropical reef parameters: 24-27 C (75-81 F), pH 8.1-8.4, salinity 1.023-1.025 SG, dKH 8-12. Provide moderate flow and plenty of live rock with caves and overhangs for grazing and security; standard reef lighting is fine.
Substrate
Fine sand bed with abundant live rock works best, as the rockwork hosts the microfauna (worms, pods) this fish grazes on. Aquascape with caves and crevices for retreat.
Equipment & setup
Use efficient biological filtration plus a protein skimmer, a reliable heater, and moderate flow from powerheads. Standard reef LED lighting suffices; the priority is a stable, mature system rather than intense light.
Diet
Carnivore that picks continuously at small invertebrates with its tubular mouth. Wild diet is benthic worms, small crustaceans and coral polyps. In captivity wean it onto live brine and blackworms, then frozen mysis, enriched brine and finely chopped clam/mussel; many specimens starve if kept in a sterile tank, so a rock-rich system with copepods and worms greatly improves survival. Feed several small meals daily.
Behavior & temperament
Peaceful and somewhat timid; reef-safe with caution. It will eat Aiptasia and tubeworms but may also nip clam mantles, zoanthids, soft corals and other sessile inverts, so it is not fully reef-safe. Keep one per tank unless a confirmed pair; combine with calm tankmates and avoid aggressive or fast-feeding fish that outcompete it for food.
Health
Stress-prone and susceptible to marine ich (Cryptocaryon) and marine velvet (Amyloodinium); the long snout is easily damaged. Most losses are from starvation and shipping/handling stress rather than disease. Quarantine before adding, and select active fish that are already eating in the store.
Tips, DIY & hacks
Drip-acclimate slowly and add to an established tank that already has copepod and worm populations. To trial Aiptasia control, confirm the fish is feeding well first. Target-feed live blackworms or enriched mysis near the rockwork to coax reluctant eaters.
