Adult females can be identified by yellow tips on the spine tipped dorsal fins. The Fiji Blue Devil Damsel fish is known to eat algae as part of their main diet. They are known for their ferocious and territorial behaviour. This fish can defend a territory up to 16 feet across. The territory usually includes feeding and spawning sites and a shelter for protection from predators.

A Fiji Blue Devil Damsel fish defends its territory against fish that compete for similar environments, such as butterfly fish and surgeon fish, even if they are much larger. However, it generally ignores less competitive species like bass and groupers. Fiji Blue Devil Damsel fish stay close to the coral reef, often darting into dark crevices to hide from predators. Fiji Blue Devil Damsel fish can remain in the same colony for up to two years.