Pottsy,
Have you ever heard of the adage, "If it ain't brook don't fix it."It's always worked for me along witht he K.I.S.S. principal -- especially since I tend to be stupid at times. (Absolutely not referring to you of course).
Bill is right, you may see a difference in PH depending on what time of day you check it. Just because it is 8.4 doesn't mean you have problems. If you were raising fish intensively in a raceway e.g. trout, then you would be limited the number of consectutive raceways you would have as the ammonia would build up on you faster with a higher pH.
