0.22 Micron Filter with Casing 20 Inches is a high precision water purification filter housing complete with a 0.22 micron membrane filter cartridge that removes bacteria, microorganisms, suspended particles and other contaminants from water to an extremely high level of purity. Suitable for fish pond water treatment, hatchery water supply, aquaculture water purification and general farm water treatment, this filter provides hospital-grade water filtration that protects your fish from waterborne pathogens.