The invention relates to a method and a device for reducing scale formation and/or corrosion in systems which conduct liquids or are in contact with liquids. According to the invention, this is achieved without reducing the quantity of hardness constituents contained in the liquid overall, without exchanging the hardness constituents in the liquid for other cations such as e.g. hydronium, sodium or potassium and without adding chemicals such as e.g. phosphates which inhibit scale formation to the liquid. Instead, scale formation is reduced by specifically shifting the molar distribution of the hardness constituents, especially the distribution proportions of the individual hardness constituents magnesium and calcium strontium and barium. According to the inventive method, proportions of the hardness constituents calcium, strontium and barium in the liquid are substituted with the proportions of the hardness constituent magnesium, In addition to efficiently reducing scale formation, the method inhibits corrosion processes in systems which conduct liquids or are in contact with liquids and reduces the extent of these processes.