[Myka]

I'm in the same boat as you Anthony. Here's my thinking:

I use IO, and when I do water changes I dose my fresh saltwater before adding it to the tank to 440 cal, 11 dKH alk (IO is 11 dKH on its own), and 1360 mag, and if I do weekly 15-20% water changes I don't have to dose the tank directly at all. Before I do my weekly water change my cal will be 400 ish, dKH will be 8 ish, and mag will be 1348 ish, and after the water change cal will be about 415, 9 dKH alk, and 1350 ppm mag. So there isn't a very large swing in the levels, and I don't have to dose the tank directly.