Coleman uses in the M6 a system with ozone and UVC light that pushes water through a chamber which kills 99.9% of microorganisms, bacteria, viruses and parasites. Â But I don't mislead people into believing that 99.9% purification is enough to eliminate all sanitizer use in their hot tub. Â The system dramatically reduces the use of sanitizers, requiring far less PPM. Â It is my understanding that the EPA will never permit a claim that any system 100% eliminates the use of some kind of sanitizer. Â An after market system sounds dubious to me. Â If it worked well then every spa dealer would sell them in their stores........capitalistic dogs that they are.........LOL