What worked best for me is using
RO water to replace evaporated water only so the minerals do not get out of hand over time. I had a 45 gallon fresh water planted
CO2 tank and I did a 5 gallon tap water change every week. Whenever the water would evaporate during the week I replaced it with
RO water to keep things stable. This method worked well for growing dwarf hair grass because it was picky about the water. Also where you live makes a difference in what plants will thrive in your tank because the water has different or more/less minerals than other places. If you want to use just
RO water you will have to supplement the the tank to replace all the minerals that were stripped out of it during the
RO process. For me it's easier to just use tap water for water changes and
RO water to replace evaporated water. Hope this helps.
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