Blue and yellow with a ringed blue spot on the forehead, which is the crown the name refers to and the character that separates it from the blue angelfish.
To about 45 cm, blue-green with yellow-rimmed scales, bright yellow pectoral fins and a yellow tail, and a dark blue crown on the forehead ringed in brilliant blue. That crown is the whole identification: the blue angelfish, which is otherwise similar, does not have it, and the two hybridise, so an animal with a partial or broken crown is likely to be a hybrid rather than a poorly marked queen.
Adults hold a territory and move in pairs, and the pair stays together. It feeds almost entirely on sponge, so it is found by searching the sponge on the reef face rather than by following the fish, and it keeps moving and turns side-on to a diver, which is why most photographs of one are of its flank. Juveniles are dark blue with vertical blue and yellow bars and clean other fish at a fixed station, so a small striped angelfish being visited by larger fish is a juvenile queen or grey angelfish rather than a different species.
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.