A dense school of Blue Tang graze across the reef. Surgeonfish, like these tang, feed on algae and are often found in packs, moving from one coral head to the next like locusts, cleaning the reef of algae.

Like other surgeonfish, the Blue Tang has a barb of sorts at the base of its caudal - or tail - fin that can extend for defense from predators. Notice the small yellow spot against the otherwise blue skin.