A fluid pump assembly is used in combination with a container having a wall. The pump assembly comprises a first casing disposed outside the container in contact with the wall, a first magnetic assembly mounted to the first casing and operatively associated with a drive motor, a second casing disposed inside the container in contact with the wall, and a second magnetic assembly mounted to the second casing and operatively associated with an propeller. The first magnetic assembly includes a rotatable magnetic drive member drivingly coupled to the drive motor. The magnetic drive member is magnetically coupled to the magnetic driven member through the wall for imparting a rotary driving force of the drive motor to the propeller. Furthermore, the second casing is detachably connected to the second side of the wall of the container solely by magnetic attraction force between the first and second magnetic assemblies.