Emperor angelfish

As its name suggests, the juvenile fish has a completely different coloration than the sexually mature adult; while it is dark blue with circular white markings early in life, the adult’s yellowish body is crisscrossed by bluish-gray lines. The reason for this color difference is that adult individuals do not view the juveniles as rivals and do not chase them away. It is mainly found in the clear waters of coral reefs.
 Adults often live in pairs. They feed primarily on sponges, tunicates, and other organisms. Both juveniles and adults have been observed cleaning larger fish and sharks. It is a long-lived fish; the oldest known individual died at the age of 14.