Sea goldies, Great Barrier Reef, Queensland, Australia

These small, bright fish in our photo are called sea goldies. They live in warm tropical oceans and gather in large groups near coral reefs. All sea goldies are born female, but some of them will turn into males as they grow up. Each male usually has a group of five to 10 females around them, but when the male fish dies or disappears, the largest female changes sex to replace the missing male. You can tell the difference by their colour. Females are bright orange and have a purple stripe behind their eyes, while males are more reddish or purple.
© Gary Bell/Minden Pictures