Vinegar or lemon juice work in a pinch, but no good long-term. My wellwater comes out at 8.0 ph, so I use phosphoric acid to bring it into range. (General Hydroponics phDown) Available at finer hydro shops and websites world-wide.

I try to use the proper tool for the job. Seems to work best that way...especially in the growroom. If it isn't formulated for the garden, I don't use it.
Unsulphered molasses being the only exception. :thumbsup: