Halfmoon Butterflyfish

About

The halfmoon butterflyfish (Chaetodon lunula) is one of the more recognizable butterflyfishes in the trade, wearing a broad dark band across the face that gives it the nickname "raccoon butterfly". The resemblance is hard to miss. A yellow-to-orange body is complemented by that distinctive mask, a dark saddle near the tail, and fine diagonal line patterning along the flanks. Juveniles look a little different, tending to hang around rocky inner reef areas and tide pools before shifting to the open reef as they mature. In the wild, this species ranges enormously, from East Africa across the Indo-Pacific all the way to Hawaii and the Marquesas, showing up in lagoons and on seaward reef flats from the shallows down past 30 meters. It tends to move about in pairs or loose groups and is notably nocturnal in its feeding habits, actively hunting nudibranchs, tubeworm tentacles, and other small invertebrates once the lights go down, though algae rounds out its diet as well. In the aquarium, that diet is the main challenge. This fish will go after coral polyps and ornamental invertebrates, making it a poor fit for reef tanks. In a fish-only system with varied meaty foods and some vegetable matter, an intermediate keeper with adequate space should do well with it.