Getwood65 + Clkwrk: I'm perplexed by TM's orp swings. Usually it does go down somewhat ( for me about 15mvs) after a water change but goes back up in no time.
I've been using IO with very, very good results save the Alk which, as Getwood65 pointed out, does run high. Ca is also pretty low. I have to keep up with a Ca + K reactors.