Cleaner shrimp
Cleaner shrimp is a generic term for any swimming decapod crustacean that cleans other organisms of parasites. This is an example of symbiosis: Both parties benefit. The fish benefit because they have parasites removed, and the shrimp gain the nutritional value of the parasites. In many coral reefs, there are cleaning stations, with many cleaning shrimps.
This behaviour is similar to that of cleaner fish. Sometimes, cleaer shrimp join cleaner wrasse and other cleaner fish.
Cleaner shrimp are often included in salt water aquaria to keep the tank clean.