Abstract: A fuel tank, in particular for fuel-cell systems, which can feed fuel into a system via a mechanism without a pump or the like. This is achieved by a fuel tank with a fuel cavity of variable size and a mechanism for compressing the fuel cavity. The fuel cavity is preferably bounded by a cylindrical inner wall of the fuel tank, by a circular end surface of the fuel tank and by a circular, displaceable intermediate wall. The intermediate wall is forced essentially in the direction of the fuel cavity by a spring and has a form fit with the cylindrical inner wall. A feed device and a discharge device allow incorporation in a fuel line. The system also includes a control device and a method for this fuel container, which is thus enabled to have the following operating states: A. fuel-cell system is switched on: discharge valve open, feed valve closed; B. fuel-cell system is in operation: discharge valve open, feed valve open; C. fuel-cell system is switched off: discharge valve closed, feed valve open; and D.