My tanks PH is roughly 7.0-7.2 (hard to tell between the two shades), whereas my taps PH if tested straight out of the tap is in the mid-high 8's. Now I've read that the proper way to determine your tap waters PH is to let it sit overnight, preferably with an airstone to let the water oxygenate. I went ahead and did that, and it tests at about 7.6 after sitting for roughly 12 hours. My question is, is it safe to perform PWC's straight from the tap (I'm concerned since its PH is significantly higher than my tank, until the water sits for a bit that is) or should I be letting it sit for 24 hours before performing water changes.. I definitely wouldn't want to cause a rapid PH change and have my fish go into shock.