A fluid driven tank cleaning which includes a housing having a fluid receiving chamber, and inlet for connecting the receiving chamber to a source of fluid under pressure, and a secondary chamber separated from the receiving chamber by a common wall as a primary drive shaft rotatably mounted within the receiving chamber. A drive impeller is connected to the primary drive shaft and disposed within the inlet is provided for rotating the primary drive shaft in response to fluid entering the housing. A second drive shaft is rotatably mounted within the secondary chamber. A magnetic drive coupler is provided for magnetically coupling the primary shaft with the secondary shaft such that the secondary shaft will rotate in response to rotation of the primary shaft. A fluid nozzle assembly is rotatably mounted to the housing and is fluidly connected to the receiving chamber. A drive train is provided for rotating the fluid nozzle assembly in response to the rotation of the secondary shaft is also provided.