Cleaner fish
Small fish that eat parasites and dead skin off larger fish, which visit their cleaning stations on the reef.
Also: cleaning station, cleaner wrasse
On coral reefs, the bluestreak cleaner wrasse and several gobies run cleaning stations: set spots where groupers, moray eels, manta rays and even sharks come and hold still, mouths and gills open, while the small cleaners pick off parasites, mucus and dead tissue. The big fish get a cleaning and the cleaners get food, so both gain. Some cleaners cheat by biting healthy mucus, and their clients chase them for it. A blenny that looks like the cleaner wrasse uses the disguise to bite visitors. Salmon farms in Norway and Scotland use lumpsuckers and wrasses to eat sea lice.