Recently, during one of our pre-dive briefings, by Michelle, the manager of fishes at the Shedd Aquarium, I learned an interesting fact about the Angelfish. 

There are about 80 species of Angel Fish in the oceans.  Some of these species are very aggressive and territorial fish (such as the Emperor Angel Fish above) that will protect their territory to the point of eating it’s own young.  So nature has helped out, when new Angelfish are born they exhibit different colors than the adults.  This color difference protects the young so the adults don’t consider them a threat.  As the fish matures they change to the adult colors. 

As we know some marine life such as the octopus and seahorses have the ability to change to their environment for protection and hunting.  The Angle Fish is born one color for protection and then changes as they grow older.   They cannot control their color change as the octopus and seahorse.