Labroides dimidiatus, the common cleaner wrasse, is a small, tropical, reef-dwelling fish. The name “cleaner” comes from the wrasse’s habit of cleaning parasites, dead skin and other potentially troublesome elements off the skin of other fish. These things are the only food a cleaner wrasse naturally eats. The common cleaner wrasse shares the genus Labroides with four other species, all of which are also cleaner fish, but the name “cleaner wrasse,” with no further description, normally refers to Labroides dimidiatus.
“Bluestreak cleaner wrasse,” an alternative common name for the fish, describes its coloring. A black band runs horizontally along the middle of each side of the fish, with white on the underside and a vivid blue above and on the back. Some deep-water populations have yellow rather than blue backs. They reach a maximum length of 5½ inches (14 cm) and have narrow bodies.
The common cleaner wrasse lives on reefs in the Indo-Pacific tropical region, where it usually is found at a depth of 3 to 100 feet (about 1 to 30 m), sometimes to 130 feet (about 40 m). At the reef, the common cleaner wrasse sets up a cleaning station, a consistent place where other fish can come and be cleaned of bothersome skin problems. Cleaning stations may be set up by a pair of adults or a group of female adults with one male. Sometimes groups of juveniles will set up a feeding station. The fish are protogynous hermaphrodites, which means that if the male disappears from the group the dominant female will take its place and become a biological male.
Cleaner wrasses are obligate cleaners, which means they must depend on cleaning activity for food. They have a very low rate of survival in captivity because their limited natural diet means that they are often difficult or impossible to train to take other food. Those that will accept other food may still be malnourished because the nutritional profile of their diet in captivity does not match that of their natural diet.
Outside of food, the cleaner wrasse requires the same water temperatures and quality as most reef dwellers. Any tank 20 gallons or larger in size is suitable as long as it has plenty of rock groups for the fish to hide in and find places to set up a cleaning station. It is very peaceful with other fish but may be injured or eaten by fish who do not naturally recognize cleaning behavior.