The Flagfin Angelfish (Apolemichthys trimaculatus) distinguishes itself by its intensive yellow body colouring and its eye-catching intense blue coloured mouth. Mostly in pairs it lives in the coral reefs of the Indo-Pacific Ocean and feeds on sponges and small crabs. Because of its attractive appearance this 15-30 cm fish is a very popular guest in aquariums around the world. Interestingly the Flagfin Angelfish is capable of developing its sex after birth. Probably it possesses the ability to adapt itself to the number of the already existent fish of the same sex in its environment.