I heard this because it's too clean, causing an imbalance in the soil. Though I'm torn between using filtered glacier ice water from the dispenser at the supermarket and the tap water:
my tap water:
170 ppm which is just fine and not too high though it probably has chlorine, chloramine and flouride in it (LA city water)
pH is about 7.1 (too high)
glacier rise RO water from supermarket water dispenser:
006 ppm (maybe too low?)
though pH seems to be around 6.4 - 6.8 which is perfect
i plan to use fox farms or roots soil for my indoor grow. Flouride, chloramine and chlorine don't exactly sound too great , though does super clean water indeed "leach" beneficial minerals or nutrients from soil...