Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The problem is not primarily the pH, it is the mineral levels.
Blend your tap water with reverse osmosis water until the GH and KH are roughly 3 German degrees of hardness. This might be a cup or two of tap water per gallon of RO.
Then let the mix stand in a bucket with some peat moss. You can add a small fountain pump to circulate the water. Overnight ought to be enough.
You will need to make enough of this water to fill the tank, then every time you want to do a water change you will need to repeat this.
Top off the tank with pure RO water.