Brilliant blue with a yellow tail, in loose clouds over rubble.
To about 9 cm, brilliant blue over the head, back and flanks with a yellow tail and yellow on the lower body, the extent of the yellow varying between populations. The blue devil damselfish is deeper-bodied and, in the male, has an orange tail; the neon damsel is slimmer and forms loose aggregations rather than holding individual territories in rubble.
Groups of tens to hundreds hover a short distance above rubble and reef edges taking plankton and drop into the rubble when pressed. It is one of the more visually striking common fish on these sites and is difficult to photograph well because the blue saturates under strobe light; angling the strobes and reducing power helps more than getting closer. Recorded from about 1 to 15 m.
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.