A filter installation and method, especially a seawater filter installation and method, includes at least one fluid line (18,20) for transporting a biological fluid, a filter device (54) mounted in the fluid line with at least one filter element (22) in a filter housing (10), and a device for biological decontamination. The device for biological decontamination contains active substances that can be introduced into the filter housing (10), such as inert gases or special metals, ensuring that toxic impurities cannot enter. The active substances used are ecofriendly unlike chemically produced fungicides and herbicides.