Bluestreak cleaner wrasse

A small blue and black fish that runs a cleaning station on the reef, eating parasites and dead tissue off other fish. Clients arrive, adopt a still posture with fins spread and gills open, and wait their turn, including groupers and morays that would eat the cleaner in any other context.

The station is a fixed location that the same wrasse works for years, and the reef's fish know exactly where it is.