A potassium aluminosilicate is used as a filtration media for filtering water to remove dissolved oxygen, hardness and other dissolved gases and impurities from the water, such as ammonia, hydrogen, hydrogen sulfide and sodium sulfite. The particular potassium aluminosilicate is a mesoporous amorphous material formed under ultraviolet light or sunlight to produce pore sizes of 60 .ANG. to 250 .ANG. at ambient temperatures (20.degree. C.-35.degree. C.) and in a low relative humidity (5%-20%). Sodium may be displaced in the zeolite media by potassium so that advantageous removal of impurities in the water occurs without introducing sodium into the water. The potassium aluminosilicate of the present invention may be used as a second stage filter to a first stage filter composed of strong base anion media charge with potassium carbonate or bicarbonate.