The present invention concerns a pump adjusting method and a membrane pump having a pumping chamber, a pressure and a suction connection, wherein the pressure and the suction connections are connected to the pumping chamber, a hydraulic chamber, wherein the pumping chamber and hydraulic chamber are separated from each other by a membrane, wherein a pulsating working fluid pressure can be applied to the hydraulic chamber which can be filled with a working fluid, wherein the membrane is moved between a first and second chamber positions of different volumes, wherein the chamber is connected to a working fluid reservoir, wherein the membrane comprises exchangeable spring elements exerting different forces on the membrane. The force which is exerted by the spring element on the membrane in the direction of the second position can be adjusted.