Minimizing fish stress from pH shift after water change
So...my tap water's pH is usually around 7; my tank's pH likes to level out around 5.6 after CO2 is injected. After a 50% water change, I notice the pH increases to near 6.76 or so. It takes only a few hours for the pH to return to normal. I have no animal life in the tank (at least none that I care about - see the words beneath my user name), but I'm concerned that when I do have things that I don't want to kill in the tank such a drastic shift in pH will have negative consequences on their overall health, or at least their happiness. Am I over-thinking the potential consequences of pH shifts, here?