Gary Bell/ Oceanwide / Whitemouth Moray (Gymnothorax meleagris) being cleaned by Cleaner Wrasse (Labroides sp) juvenile, Christmas Island, Australia

Shane Gross / Pelagic thresher shark (Alopias pelagicus) cleaned by a Bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

Shane Gross / Pelagic thresher shark (Alopias pelagicus) being cleaned by a bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

David Fleetham / Cleaner wrasse (Labroides dimidiatus) swimming alongside Golden damsel (Amblyglyphidodon aureus) looking for parasites, Fiji, Pacific Ocean.

Alex Mustard / Harlequin sweetlips (Plectorhinchus chaetodonoides) cleaned by a pair of bluestreak cleaner wrasse (Labroides dimidiatus). South Atoll, Tubbataha Atolls, Tubbataha Reefs Natural Park, Palawan, Philipp...

Georgette Douwma / Dead surgeonfish being 'cleaned' by a Bleusreak cleaner wrasse (Labroides dimidiatus). Many fish observed dead or dying on reefs in the Maldives, April 2012. Another episode of dying fish was in 2007....

Juergen Freund / Yellowtail fusilier (Caesio cuning) being cleaned by a Bluestreak cleaner wrasse (Labroides dimidiatus) Papua New Guinea.

Juergen Freund / Giant manta ray (Manta birostris) at a cleaning station. North Raja Ampat, West Papua, Indonesia.

Juergen Freund / Giant manta ray (Manta birostris) at a cleaning station with diver swimming behind it. North Raja Ampat, West Papua, Indonesia.

Juergen Freund / Giant manta rays (Manta birostris) at a cleaning station. North Raja Ampat, West Papua, Indonesia.

Nick Upton / Rock cook / Small mouthed wrasse (Centrolabrus exoletus) caught in a rock pool on a low tide, being taken out of a fishing net. Cornwall, UK.

Georgette Douwma / Lyretail anthias or Goldie (Pseudanthias squamipinnes) male being cleaned by a Cleaner wrasse (Labroides dimidiates). Rinca, Indonesia