Abstract: An oxygenating centrifugal pump is primarily for circulating the aerated water in a culture pond for improving water quality. The centrifugal pump generally comprises a flat-bottomed cuplike vessel having a pair of floaters for floating said pump on a water and a plurality of pipy legs for locking the vessel in a bottom of the pond. An inner hollow cylinder closed at its top end is longitudinally and rigidly mounted through a bottom wall of said vessel, an umbrella-shaped diffuser is secured to a lower periphery of said cylinder and a motor driven shaft having an impeller at its lower end portion is longitudinally mounted in said cylinder to define a diffusing passageway between said diffuser and impeller.