pH adjustment is quite important for all aquaponic systems. Try to stay with the range of 6.8 to 7.0 as much as possible. There are wide diversities of municipal water supplies that can be used as the initial water for your system.
This video shows organic ways to do pH adjustment, either up or down using easily obtainable materials. Additionally the video provides a very clear explanation of what pH is, and how the scale operates. It is not linear, every point is ten times more (or less) that the previous one.
Worth the time if you are having problems regulating the pH of your water.