Barberfish cleaning goat fish

When goat fish, normally silver Otha yellow tail, wish to be cleaned of Parasites, they go to a cleaning station "manned ' by barber fish. They then change coloured assume a vertical position, head down, over the coral. The barber fish will then swim in and pick off the parasites. It is thought that the change of colour signal to the barber fish that they are ready for leaning but also makes it much easier for the cleaners to spot the parasites