The juvenile is only 3-5 cm long and has a thin black body with neon-blue lines on head, middle of dorsal fin and upper tail base. It also has a yellow to white bar crossing the mid body. The adult is quite different. it reaches 14 cm and is mostly gray with black scale outlines and blackish fins.
Seen while snorqueling in the shoreline of Lankayan Island, Sabah (Borneo).