Abstract: Method of controlling biofouling and microorganism population levels in a water system, comprising adding to the water a redox buffer and oxidizing thereafter. The redox buffer may be a peroxide or hydrogen peroxide (H2O2), which is added to the water. The redox buffer keeps the redox potential between about 250 to 450 mV. The oxidant may include a halogenating chemical which is chosen from among the hypohalite species, such as HOCl, NaOCl, NaOBr, HOBr, OBr−, OCl−, Br2, Cl2 and acid solutions. The acid solution is selected from among those containing (Cl2+HCl), (Br2+HBr), (Br2+HCl), trichlorocyanoric acid (TCCA), bromochlorodimethyl hydantoin (BCDMH), dibromodimethyl hydantoin (DBDMH), dichlorodimethyl hydantoin (DCDMH), and other halogen agents, preferably an active chlorine donor or sodium hypochlorite (NaOCl) or hypohalide acid (HOX), such as hypochlorous acid (HOCl) or hypobromous acid (HOBr), or hypohalite ion OX, wherein X is Cl or Br, or halohydantoin.