This answered some of my questions as well. I got a used hot tub and decontaminated using Nitro's method, but when I filled it the lady at the store told me to only shock with dichlor weekly and use primarily MPS. She didn't do a good job of explaining that the Nature 2 ionizer was the reason for this and I had a test kit that didn't check MPS. I was very converned by my chlorine levels and ended up draining tub and going to the Dichlor/Bleach method. The Nature 2 thing is still equipped, should I remove it now that I'm going to the Dichlor/Bleach method? Will it be a problem or is it just mostly useless now. I never had any idea what the Nature 2 stick was for, she explained it was because the hot tub is old and the ozonator probably doesn't work anymore. It is a 2003 Tiger River Bengal. Thanks