I assume SuperThrive would acidify your pH to some extent, but have not tested it, because I don't use the stuff much - according to all my local nurseries, and a friend-of-a-friend that is a working botanist, SuperThrive is nothing more than Vit. B1, and 'urea' (urine) - urea, urine, piss, whatever, is a strong nitrogen source, (which is why peeing on your plants is a no-no) - a strong source of nitrogen like that could lower pH - I had problems with many seedlings only after trying Superthrive (as directed, only a drop or two per gallon) - I researched it pretty heavily, and I do believe that it stimulates root growth - I mix one drop per gallon when rooting clones, and have experienced great success (but, I think my recent success is because of my new bubble-cloner, and not the SuperThrive alone) - IF you decide to use it, use it in weak solutions, as the instructions suggest - :smokin: