Soil pH question...

I read that it needs to be pH 6.2-6.7 for weed growing (in soil) but my water is pH 8... I don't want to use bottled water so I'm using pH down from an aquarium supply to adjust the pH of my water... Could it be Harmful for my plants? What should I do?

Should be fine, lot's of people need to adjust the PH of their water, especially with hydro.

I would keep it super simple and get some white vinegar to bring down the ph. about 1/2 to full cap is enough for 1 gallon of water.