The present invention relates to q method for preparing a tank mix, which comprises the step of contacting a pesticide formulation, water, and a tank mix adjuvant, wherein the tank mix adjuvant comprises a base selected from a carbonate and/or a phosphate, and wherein the tank mix adjuvant is present in form of a particulate solid, which contains at least 10 wt % of the base. The invention also relates to a use of a tank mix adjuvant for increasing the efficacy of a pesticide, wherein the tank mix adjuvant comprises a base selected from a carbonate and/or a phosphate, and wherein the tank mix adjuvant is present in form of a particulate solid, which contains at least 10 wt % of the base; to a tank mix adjuvant which comprises an auxiliary and a base selected from a carbonate and/or a phosphate, wherein the tank mix adjuvant is present in form in form of a particulate solid, which contains at least 10 wt % of the base; and to a method of controlling phytopathogenic fungi and/or undesired vegetation and/or undesired insect or mite attack and/or for regulating the growth of plants, wherein the tank mix is allowed to act on the respective pests, their environment or the plants to be protected from the respective pest, on the soil and/or on undesired plants and/or the crop plants and/or their environment.