Update:
So after a 75% water removal, I put in r/o water to fill the tank. The resulting test brought the hardness down to a medium high level. So it appears that I’ll never use my tap water to do water changes or top offs. Fortunately, I caught it in the first of my nano tanks before my fish arrived.
Will the “Super Duper Hard water” affect my plants too much? They were in it for about two weeks. It’s my first planted tank so I went with those plants marked on the Aq.Coop website as “easy” to care for.
thoughts?