Glassfish or Sweepers, Parapriacanthus ransonneti
Also known as glass fish and golden sweepers, you find dense schools of these small fish throughout the Indo-Pacific, from the Red Sea to Australia. They like shady places during the day: wrecks, overhangs and caves. At night they venture out to feed on zooplankton.
Sweepers have large eyes and a single fin on their backs.. They are 10 cm long with yellow heads, peach-coloured bodies and a distinct lateral line running from head to forked-tail.
The pygmy sweepers have light-emitting compounds in their guts, presumably gained from food they have eaten.
Pygmy sweepers living in the Red Sea used to be known as Parapriacanthus guentheri, but it is now thought that there is just one species and Parapriacanthus guentheri is an obsolete name.
Photo copyright Tim Nicholson.
Taken in the Egyptian Red Sea.
Coral Reef Fishes, Indo-Pacific and Caribbean, by Ewald Lieske and Robert Myers, Harper Collins
The Underwater Photographer: Digital and Traditional Techniques, by Martin Edge, Paperback, 536 pages