Wrasses are carnivorous. Their diet consists primarily of parasitic copepods and other invertebrates that are taken from the mouth and gill openings of larger fish. They also feed occasionally on free-swimming crustaceans.
Blue streak wrasses are known as common cleaner fish that set up cleaning stations on various parts of coral reefs, usually 3-10ft. deep. They attract larger fish to their stations by making strange, oscillatory swimming movements, and the fish then stop to get cleaned. Wrasses enter the mouth and gill openings and remove any ectoparasites and diseased tissue. The larger fish not only refrain from devouring these small cleaner fish, but actually readily open their mouth and gill cavities so that they are able to clean.
This is clearly a mutualistic relationship between cleaner wrasses and various larger fish of the ocean (Grant, 1978).