People fret far too much over pH. Screwing with your pH is _far_ worse for you fish in most cases than keeping stable, if slightly less than ideal, pH.
pH is the number of ions (+ve or -ve) in your water.
You should worry about pH level of your water unless you are trying to breed. Many of the fishes we buy today are tank bred and thus able to handle wider range of pH ranges. Simply keep in eye for pH crashes as this could lead to disaster with build up of nitric acid {i.e. converted from NO3 and NH3)