Planted Tank Guru
Join Date: Nov 2009
Location: Missouri united states
Well ,let us say that your tank now sit's at 7.2 pH.
If your tapwater is higher, or near same,then this would be less dramatic change than previously = good news for fish.
If you were to lower the pH ,then tapwater with higher pH at water changes would be more dramatic,possibly stressful.(due to sudden increase in GH).
Fishes will adapt to the pH you have so long as it is stable,consistent, and this is far more important than chasing some magic number.
PH is but a number that fish don't feel.It is the sudden change in hardness that affect's the fish more so than the pH.
pH is usually, associated with mineral content,buffering capabilities,but most folk's don't test GH,KH, and instead look to pH which as mentioned isn't really as important as the hardness (GH) or KH (buffering capability).
My two cent's.