The invention relates to aqueous suspensions or dispersions (slurries) of minerals and/or fillers and/or pigments containing one or more dialdehydes and one or more formaldehyde cleavers, and to the use of mixtures consisting of one or more dialdehydes and of one or more formaldehyde cleavers for stabilizing aqueous suspensions or dispersions of minerals and/or fillers and/or pigments (slurries) with regard to infestation or deterioration by microorganisms.