The present invention relates to a mixing impeller for an agitator. The impeller has a body that may be disc-shape. The impeller has a plurality of radially spaced-apart, longitudinally curved, channel-shaped outer vanes connected to and extending outwards from the body in a plurality of different directions. A first one of the outer vanes has a distal end at least partially facing above the body. A second one of the outer vanes has a distal end at least partially facing below the body. A third one of the outer vanes has a distal end at least partially facing tangential to the body.