Richard Robinson / Grey Unicornfish (Naso caesius) and Sleek Unicorn fish (Naso hexacanthus ) school at Banc Lorne, New Caledonia.

Pascal Kobeh / School of Yellowback fusiliers (Caesio xanthonota) and Bluekeel unicornfish (Naso hexacanthus) Madagascar. Indian Ocean.

Georgette Douwma / Surgeonfish, composite image on black background, Yellowtail tang (Zebrasoma xanthurum), Powder-blue surgeonfish (Acanthurus leucosternon), Elongate surgeonfish (Acanthurus mata), Striped surgeonfish...

Georgette Douwma / Blacktongue unicornfish (Naso hexacanthus) composite image showing variation in marking on black background, Maldives, Indian Ocean.

Georgette Douwma / Surgeonfish composite image on black background, Bluespine surgeonfish (Naso unicornis), Striped surgeonfish (Acanthurus lineatus), Sailffin tang (Zebrasoma veliferum) juvenile, Mimic surgeonfish (Aca...

David Fleetham / Sleek unicornfish (Naso hexacanthus) at a cleaning station with a Hawaiian cleaner wrasse (Labroides phthirophagus), Molokini Islet, Maui, Hawaii, Pacific Ocean.

David Fleetham / Three Sleek unicornfish (Naso hexacanthus) at a cleaning station with a endemic Saddle wrasse, (Thalassoma duperrey) Hawaii.

David Fleetham / Sleek unicornfish (Naso hexacanthus) which has turned a darker than normal colour to help an endemic Hawaiian cleaner wrasse, (Labroides phthirophagus) spot parasites, Hawaii.