A composition comprising:(a) A 3-isothiazolone compound(b) a stabilizing amount of a metal salt, said metal salts selected from the group where the cation is copper, zinc, manganese, ferrous or ferric, and the anion is selected from the group consisting of an organic carboxylic acid of at least of six carbon atoms, EDTA, 8-hydroxyquinolinate, gluconate, o-phenanthroline, quinolinate, N,N-bis(2-hydroxy-5-sulfobenzyl) glycine, lignosulfonate polymers, and polyacrylates; and(c) a locus to be protected against the growth of algae, bacteria, or fungi, selected from the group consisting of:(i) a metal working fluid (MWF) comprising at least one component selected from the group consisting of an alkanolamine, a petroleum sulfonate emulsifier, a boric acid ester or boric acid amide, a corrosion inhibitor, and a fatty acid;(ii) cooling tower water comprising corrosion inhibitors or scale inhibitors,(iii) laundry dish water;(iv) a cosmetic formulation;(v) a fuel system;(vi) an emulsion;(vii) a solid protective or decorative film.