Thanks Tom,

I'm just now getting back to trying to get this tank in shape again, and revisiting things I'd tried before.

The water here has 83ppm Ca and 50ppm Mg (per water quality report and confirmed by testing) actual ppm not as CaCO3. I've cut it in half with RO and could cut it in half again to get the Mg down close to 12ppm. But the Ca:Mg ratio is still out of whack and I didn't know if it was worth bothering with. I can add CaCl to add Ca back and get the ratio closer to 3:1 Ca:Mg but only if it's necessary.

TW

EDIT: It was someone else that brought this up, and when I asked for a reference they pointed at that thread you mentioned with Edward's r wallachi. And so the myth propagates like a weed.