The product comprises a solid biocide and a composite material (11) for the absorption of impurities (5.1,5.2) and release of active substances (13.1,13.2). The solid biocide is so formed that it produces a germ-killing effect on the microorganisms (4.1) with the contact, particularly with the surface contact, with microorganisms due to a catalytic mechanism. The composite material is so formed that it absorbed impurities from the fluid (6) and/or release active substances, which reduce the impurities and/or sterilize the fluid. An independent claim is also included for a method for cleaning a fluid with products, which involves treating the composite material for the absorption and release of active substances in former step, and shifting the surface-active solid biocide in later step. ACTIVITY : Antimicrobial. MECHANISM OF ACTION : None given.