Saddleback Butterflyfish

Geographic Origin and Biotope: Widespread in the tropical Indo-Pacific, from Sri Lanka and Cocos-Keeling Islands to Hawaii, the Marquesas, and Tuamotu, north to southern Japan, and south to New South Wales (Australia). Inhabits coral-rich lagoons and seaward reefs down to 30 meters.

Taxonomy and Morphology: Member of the family Chaetodontidae, subgenus Rabdophorus. A large butterflyfish growing up to 30 cm in length. Adults develop a long trailing filament extending from the soft portion of the dorsal fin.

Social Behavior: Diurnal species, found singly or in stable monogamous pairs that defend large territories. Generally peaceful toward other families, but territorial toward conspecifics or similarly patterned species.

Coloration and Sexual Dimorphism: Silvery-grey body with wavy blue lines on the lower half. Features a large, white-edged black saddle-like patch on the upper rear of the body and dorsal fin. No visible sexual dimorphism exists.

Aquarium Setup: Demands a very large aquarium of at least 600 liters for adults, offering vast swimming space and a sturdy live rock structure. A secure lid is mandatory as they are highly prone to jumping.

Diet and Feeding: Omnivore. Feeds naturally on filamentous algae, coral polyps, fish eggs, and small invertebrates. Feed 3–4 times daily with mysis, brine shrimp, clams, spirulina, and nori. May take time to accept pellets.

Water Quality: Pristine and stable water parameters. Temperature 24–28°C, pH 8.1–8.4, salinity SG 1.020–1.025, GH 15–25, and KH 8–12. High biological load requires robust filtration and protein skimming.

Compatibility and Tankmates: Best kept in large Fish-Only With Live Rock (FOWLR) systems. Not reef-safe under any circumstances, as it will decimate hard and soft corals, anemones, feather dusters, and small shrimps.

Aquarium Reproduction: Undocumented in captivity due to extreme difficulties in rearing its pelagic larvae. Monogamous broadcast spawners in the wild.

Risks and Diseases: Highly susceptible to marine velvet (Oodinium) and ich (Cryptocaryon) if stressed. Demands strict quarantine and patience during feeding acclimation.