Absolutely nothing wrong with the PMDD recipe shown there. I've used
it since it first came out. By "old" I didn't mean to imply something
"new." I meant "old" as in "venerable, tried, and true." As in "an
old friend," which needn't imply a "new friend." (I love how language
works.) The old, tried and true PMDD recipe has chelated Fe, trace
elements, lots of magnesium sulfate, potassium sulfate, and
(optionally) potassium nitrate. After reading here and elsewhere, I've
learned that many people are adding micro nutrients independently of
the macros. My specific question concerned my local hard water. After
checking the water testing reports for my area, I don't think Mg and Ca
will be in short supply with regular water changes.