The commonest large angelfish on sheltered slopes; the juvenile is a set of white half-circles.
Adults reach about 38 cm and are dull by angelfish standards: olive to brown-grey, finely speckled, with a blue-edged gill spine, blue lips and blue trailing edges to the fins. The juvenile is the striking stage — black with alternating white and pale blue bars that curve into half-circles at the tail, the arrangement that gives the fish its other common name. The intermediate stage, around 15 cm, carries fragments of both patterns at once.
Juveniles hold to a fixed shelter in shallow rubble, under jetties and around wreckage, and are among the easier large-angelfish juveniles to photograph because they do not leave their patch. Adults range widely across a slope, feed on sponges and algae, and are wary. In the Lembeh Strait the species is regularly recorded on the coral heads at the ends of muck sites rather than on the sand itself.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.