Arsenic combines with iron, and is then retained by the AS-FE-MN media, which is attracted to metals. If there is no iron in the water, iron chloride is added to the iron to combine with the iron. If your stallion is high, it may be necessary to add iron chloride. In a laboratory test, iron chloride was added in small quantities to well water containing approximately 78 PPB arsenic, and then passed through AS-FE-MN media. According to the results obtained, it has been proven that the AS-FE-MN medium reduces the arsenic content from 78 PPB to <1 PPB. In large-scale applications, the AS-FE-MN media is simply re-commuted with backwashing with clean chlorinated water. It does not need regeneration like the classic Greensand media.