Merten's Butterflyfish

About

The Atoll Butterflyfish (Chaetodon mertensii) is a mid-sized Pacific butterflyfish with a vivid orange vertical bar crossing the rear portion of its body, set against a pearlescent white flank pattern. A combination that makes it fairly easy to identify in the field. Its range runs from the Ryukyu Islands and the Philippines across to remote outposts like Lord Howe, Rapa, and the Tuamotu archipelago, where it inhabits deep lagoons and the outer faces of seaward reefs. In those environments it tends to be found alone or in bonded pairs, foraging across the substrate for algae and small invertebrates. Interestingly, this species occupies a role in the Pacific that closely related species fill elsewhere. Chaetodon madagascariensis takes its place in the Indian Ocean, and Chaetodon xanthurus overlaps it in parts of Southeast Asia, with the two occasionally producing hybrids where their ranges meet. In the aquarium, the Atoll Butterflyfish is considered an intermediate-level fish. Not the most demanding of the butterflyfishes, but it needs a spacious, well-established system with good water quality and a varied diet. It generally settles well when given room to move and consistent feeding, and its natural pairing behavior means it may fare better with a companion of the same species.