FROG Test Strips precisely measure chlorine or bromine levels at the low end of the scale - something ordinary test strips won"t do. * Such accuracy is important since FROG Mineral Systems are designed to operate at just .5 parts per million of chlorine for pools or 1 part per million of bromine for spas. * In 15 seconds, you can know precisely what level of chlorine or bromine is in the water, as well as whether your pH and Total Alkalinity are balanced.