I know that they are not going to notice the rising of the pH in the day following a water change. They WILL notice the drop in pH at the very moment I am doing a water change. I noticed this the other day when I did a 30% PWC. They were jetting across the tank for about 1.5hrs afterwards. This was the first PWC I've done since I finished cycling, and during the cycle was doing PWC's 1-2 times a day. I guess they never experienced that big of a pH drop during a PWC previously. Then again, when I've tested the water before, it was always around 7.5 which isn't much different. ^.- I was doing the PWC to start getting rid of cloudy meds and salt from the treatments I'd been doing for the past few weeks. Maybe the decrease in salt, meds, and pH all combined wigged them out a little.
I am going to get a large container to let my tap water sit in before water changes I think.