I believe the N2 manual recommends a min level of 0.5ppm. Â I've been targeting 0.5 - 1.0ppm on our tub with N2. Â Our tub also has a copper ionizer, so I get some additional mineral help. Â With your ozone, you should be able to follow the low chlorine recipe on page 6 of the Nature 2 manual and get great results. Â Since you have ozone, you may be able to use even less MPS. Â
I've been thinking about adding a salt based chlorine generator. Â I spoke with a couple of people at spachlorinator.com about the TechniChlor and the ColorChlor. Â I was told that those could be set to generate chlorine in low amounts like I want.