Hmm, then why does the calulator recommend 5ppm? (confused):/
although I think I will change some of the water, if for no other reason than the fact that the API chart goes up like this:
0, .25, .5, 1.0., 2.0, 4.0, 8.0
so really with a reading between 4.0 and 8.0 I have no way of knowing whether...