A medical fluid pumping system, comprising: a medical fluid pumping machine defining a cassette enclosure, the medical fluid pumping machine comprising an actuator; and a medical fluid cassette configured to be disposed within the cassette enclosure of the medical fluid pumping machine, the medical fluid cassette comprising: abase; a membrane attached to the base, the membrane and a region of the base cooperating to define a fluid pump chamber, the cassette positionable within the cassette enclosure of the medical fluid pumping machine so that the actuator is substantially aligned with the fluid pump chamber; and a member disposed within the fluid pump chamber, the member being magnetically attracted to the actuator such that the member and the actuator are configured to be coupled together with a portion of the membrane positioned between the actuator and the member when the cassette is disposed within the cassette enclosure, wherein the actuator is configured to be retracted a distance away from the base of the cassette to decouple the actuator from the member, wherein the medical fluid pumping machine comprises a decoupling post that is arranged to be received in a bore at least partially formed by the actuator as the actuator is retracted, and the decoupling post is configured to prevent movement of the member in a direction of the retracting actuator to facilitate decoupling of the actuator from the member. a medical fluid pumping machine defining a cassette enclosure, the medical fluid pumping machine comprising an actuator; and a medical fluid cassette configured to be disposed within the cassette enclosure of the medical fluid pumping machine, the medical fluid cassette comprising: abase; a membrane attached to the base, the membrane and a region of the base cooperating to define a fluid pump chamber, the cassette positionable within the cassette enclosure of the medical fluid pumping machine so that the actuator is substantially aligned with the fluid pump chamber; and a member disposed within the fluid pump chamber, the member being magnetically attracted to the actuator such that the member and the actuator are configured to be coupled together with a portion of the membrane positioned between the actuator and the member when the cassette is disposed within the cassette enclosure, wherein the actuator is configured to be retracted a distance away from the base of the cassette to decouple the actuator from the member, wherein the medical fluid pumping machine comprises a decoupling post that is arranged to be received in a bore at least partially formed by the actuator as the actuator is retracted, and the decoupling post is configured to prevent movement of the member in a direction of the retracting actuator to facilitate decoupling of the actuator from the member. abase; a membrane attached to the base, the membrane and a region of the base cooperating to define a fluid pump chamber, the cassette positionable within the cassette enclosure of the medical fluid pumping machine so that the actuator is substantially aligned with the fluid pump chamber; and a member disposed within the fluid pump chamber, the member being magnetically attracted to the actuator such that the member and the actuator are configured to be coupled together with a portion of the membrane positioned between the actuator and the member when the cassette is disposed within the cassette enclosure, wherein the actuator is configured to be retracted a distance away from the base of the cassette to decouple the actuator from the member, wherein the medical fluid pumping machine comprises a decoupling post that is arranged to be received in a bore at least partially formed by the actuator as the actuator is retracted, and the decoupling post is configured to prevent movement of the member in a direction of the retracting actuator to facilitate decoupling of the actuator from the member.