Some tap water is okay, mine is only 35 PPM,which is quite pure. But yes, you do have to watch for hard water, which is loaded with calcium, iron, and chlorine(the worst one). Anyway, if you want to lower the PH, you can use a little lemon juice, or some vinegar. Some claim white is best, and other claim that cider is best, so I imagine that either would be fine. Better yet, go to the local Walmart and buy some 'PH down' for aquariums. Just make sure it's phosphate free, and you'll be good to go. Or, your best option would be to order a bottle off Ebay or something. It's pretty cheap, like $15 for a bottle, which'll last quite awhile.