Photo copyright Tim Nicholson.
Taken on Little Brother in the Egyptian Red Sea.
Lionfish (Turkeyfish), Pterois miles, over soft corals.

Found in the Red Sea and Indian Ocean to the Andaman Sea. Elsewhere replaced by the very similar P. volitans. Usually 11 dorsal rays (those on the top of the fish). A sting from this fish can be very painful, and possibly fatal. Often shelter under ledges during the day, more active at dusk and during the night when feed on fishes and crustaceans. Lionfish use their non-stinging pectoral fins to shepherd fish into their mouths. Poisonous spines allow the fish to be conspicously coloured, warning predators to keep their distance.

Further Reading
Coral Reef Fishes, Indo-Pacific and Caribbean by Ewald Lieske and Robert Myers, Harper Collins
The fascinating secrets of Oceans & Islands, The Reader's Digest Association
Underwater Photographer by Martin Edge, Focal Press