An apparatus for activating or cleaning filter tube wells with a filter tube includes a first and second volume bodies, which are substantially adapted to the inside diameter of the filter tube and on the outer circumferential surfaces thereof are designed radially flexibly with respect to the well longitudinal axis such that a sealing effect is achieved between the outer circumferential surfaces of the respective volume bodies and the inside wall of the filter tube. A removal chamber, which can be hydraulically connected to a pump device, is formed between the first and second volume bodies and the inside wall of the filter tube. At least one equalizing tube completely penetrates the removal chamber in the longitudinal direction of the apparatus such that a hydraulic connection is established between the respective regions that adjoin the outer faces of the two volume bodies disposed opposite of the removal chamber.