Media for selectively removing radium ions from water where manganese oxide (DMO) has been dispersed in a cation ion exchange resin (gel or macroporous) to adsorb radium ions. The media is manufactured by precipitating a soluble manganese (II) salt such as manganous sulfate with a permanganate salt such as sodium permanganate inside a strong acid cation (SAC) to form a resin containing highly dispersed manganese oxides. The resin is then post treated with a reducing agent such as sodium metabisulfite (Na.sub.2S.sub.2O.sub.2) to prevent the leaching of soluble manganese from the resin. The reducing treatment ensures that soluble manganese species will be converted into an insoluble oxide form.