this is true if your doing a hydro grow. i dont do hydro, just soil. it works for me just fine in soil even though it probably dosnt need it. good point punk.I wouldn't recommend either of those. Take baking soda: Sodium Bicarbonate...which will only compound your problems. Vinegar is not a stable acid, so when you think you've balanced everything, a day or two later, the ph in your resevoir or bucket-o-water is out of wack again. I don't have the chemistry major to tell you precisely why just not to do it. A liter of ph-up and down is only about 10 bucks each and will last the average home grower for years.