Blue Tang mature

These fish have three color phases. In their juvenile phase, they are bright yellow, changing to a mixture of yellow and blue during adolescence. They may also have blue crescents above and below the pupils of their eyes. They may also be spotted with blue or have a yellow body and blue fins.

As these fish mature into the intermediate phase, their color darkens to a bright blue or purplish-gray with a yellow caudal (tail) fin. Gray longitudinal lines are located in their flank region with blue dorsal and anal fins banded with orange-brown diagonal lines. Their caudal spines become yellow to pale yellow or white. At night, blue tangs display white vertical stripes.

Adult blue tangs are deep blue to purplish-blue with yellow caudal spines. The change from juvenile to intermediate to adult coloration is not size-dependent as some fish in the juvenile yellow phase may be larger than the adult blue phase.