Huh?!!

[SCMurphy]

They certainly don't downstream of the limestone springs in FL. I could see where you have to make sure that the plants don't use up the Ca and Mg on you. My college limnology class went to a couple lakes on trips and the prof pointed out the difference in an invasive myriophylum in two of the lakes, one hard water the other soft water. The plant was 'crispier' in the hard water lake. The plants were thriving in both lakes.