Method for killing water borne microorganisms

A method for killing water borne microorganisms comprises reacting two electrolytically-reactive elemental metals in water to dissolve sufficient metal ions to kill algae and coliform bacteria, without making the water unsafe for human use. Lead, copper and zinc are examples of such metals. Apparatus for performing the method comprises a perforated container of chips of such metals. A small version of the device can be used in toilet reservoirs to prevent the growth of microorganisms within the toilet bowl. A larger version of the device, submerged in a swimming pool, effectively prevents the growth of algae or coliform bacteria, substantially reducing or eliminating the need for chlorine. One embodiment of the device has an elongated cylindrical container with perforated side and bottom walls and a hook at its upper end for suspending the device in a swimming pool or toilet reservoir. A second embodiment of the device has a vertically elongated, broad-based container with only a lower portion of its side walls perforated. An air bubble retained inside the container when immersed in water helps keep the container upright.