you can use lemon juice to get your water ph down. that doesnt apply to tons of water of course. i use lemon juice to get the tap water ph down for watering seedlings,just one lemon is needed for a couple gallons or more water...
People use vinegar too. I've heard some claim that white is the kind to use, then others claim that cider vinegar is the stuff to use, so I assume that both'll work fine, til you can get your hands on some stuff designed for growing.
