Juvenile fish
The slender grouper is a medium fish growing to a length of about . The head occupies 40% of the total length and the mouth is large, with the lower jaw longer than the upper jaw. There are no palatine teeth, a fact which distinguishes this species from other groupers. The basic colour is pale reddish-brown liberally dotted with orange spots which are closer together on the head. There are five pale silvery blue longitudinal lines running down either side, the lower 3 reaching the tail but the upper two breaking into irregular streaks. The dorsal fin has 11 spines and 14 to 16 soft rays. The anal fin has 3 spines and 8 to 9 soft rays. Juvenile fish have vivid blue and red longitudinal stripes.