For the installation a core hole drilling or a recess through the wall of the tank is necessary. The sealing between the concrete wall and mixing rod is effected by the link seal (rigid installation) or a rubber sleeve special sealing (hydraulically adjustable installation). For the fixation of the mixer rod, when installed rigidly, supports are used inside and outside of the tank. A special designed mounting plate provides the fixation of the mixing rod when installed hydraulically adjustable. The installation is retrofittable at any time.