another way to lower Ph is to add a measured amount of distilled water or
RO water during changes. The exact amount you will have to determine as in 1 cup per gallon or more. Driftwood and peat will discolor you water with tannins for a while.
Be aware once you start this procedure (any of them) it must be continued so your PH remains stable. Even with driftwood or peat, which eventually will leach out and your PH will start going up again.
Example is that I use pure RO water and must add 1/2 gallon of my tap water to every 6 of RO water....to raise my PH to 6.4
You can do the opposite by adding X amount of Distilled or RO water to lower your Ph.
I always make approx 20 gallons at a time for water changes and store it in 7 gallon containers from one of the "mart" stores.