I dont use RO water and I never will. For every 3 gallons of RO water you get, up to 7 or 8 gallons of water is wasted. Thats horrible for the environment. Why would you take out minerals only to re-add them with Calmag afterwords? Obviously this only applies to people who have good water to begin with, but I know too many people that spend tons of money on water bills and filters using RO on water that I use with absolutely no deficiencies with a ton of different strains and growing methods and dont filter it through anything. I will argue that RO water does not hold pH stable nearly as well and I will also argue that when you get rid of all those elements and minerals, your nutrients have less to bond too. For people with algae blooms and bad water (what I consider high ppm over 250 and pH of over 7) then I think RO is neccessary but I think a ton of people could get the same results with tap water.

The more money you spend on an RO system, the longer your filters last and the less water you waste. Its worth it. You will pay the difference in water bills within a year.