Most people use RO (reverse osmoses) water from start to finish. Most tap water has many chemicals that can slow plant growth or even kill young plants. Chlorine and many other minerals common in tap water are not good for your plant.

You can get a good RO system from eBay for less then 100 bucks delivered if you just look around a little. But that is a drinking type of filter. Plant RO filters have different membranes and filters and leave in some minerals the normal drinking RO process removes that is why plant RO systems cost more. (so the manufacture say anyway)

The other thing you need to know about store bought or even home made RO drinking water is you need to put back some minerals back into the water to make it the best for plants. Thatâ??s why you add CalMag Plus to your RO drinking water it replaces the minerals the RO process removes.