Phos-Free reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. It is designed to remove phosphates. But because it combines with the other elements noted it seems that it may also reduce borates, chlorine and possibly other chemicals as well. Does anyone know what chemicals Phos-Free removes besides the Phosphates? If someone is trying to keep borates at 50 ppm, should they avoid Phos-free?