BUT to finalize your purification course of action, use UV from the 254 nanometer array(including the Steripen) to finish off the left more than cysts. Use the UV product before, Correct BEFORE you utilize the water you hav filtered. WHY, you ask. I found ha after the cysts left in http://martiniwjw24803.dsiblogger.com/11765885/not-known-facts-about-water-filter