Do you have any plans getting an RO (reverse osmosis) water filtration system for your home? It is very good for cooking, ice making, drinking and aquatic plants. The reason is because very few plants can grow in KH of 16 degrees. If you are ok with that then find how much Ca and Mg is in your water. Most waters like this don't have much Mg so you need to find out first.
No plans on R/O, I did at one time use RO to dilute my tap 50/50. But I stopped and in the last year or so, I have 3 planted tanks doing great on tap and EI dosing. But with the PPS-pro's progam of daily dosing and smaller and less frequent water changes(less waste which is why PPS is interesting to me), will the addition of Mg, be a problem?
And how does one test Calcium and Magnesium, the common Calcium test kits I see at the LFS are for salt, will they work in fresh?