Low pH Plants
Plants and fish prefer opposites when it comes to acidic or basic tank water. Plants like a lower pH (acidic). That's why you want to use a lot of aquatic plants when you cycle your tank. They use the nitrogens produced by the fish for their food.
Fish prefer a higher pH (basic). Most aquarium fish will do well in water with a pH of 6 to 8.5, as long as the level is constant. The vast majority of aquarium fish will adapt to the vast majority of public water supplies. So, pH really isn't important as long as you don't keep rare fish.
You can use commercial chemicals to change the pH, but that's risky because it's difficult to maintain a specific level. It's best to just treat the water for ammonia, chlorine and chloramine and let the fish and plants do their job of adaptation. They've been doing it for a long time.
Just a couple of thoughts.
"Fear not my child, just change the tank water."