Also called Schooling Coachman, Schooling Bannerfish, False Moorish Idol and Pennant Butterflyfish. They feed on coral polyps, tentacles of feather stars and tube worms, and reach a size of 20cm.
Found in schools along outer reef slopes and in current channels, at depths of 15 to 200m. Widespread in the Indo-Pacific region.
The photos were taken during a night dive, and the video during a day dive, both at the same location: 12m depth at Dayang Beach, Talikud Island. This spot has a large population of H. diphreutes, numbering in the hundreds.