well those ones will only tell you about where it is and if your using distilled its going to be between 7 and 8...my opinion don't even worry about it because really that will not help you very much..If your going to get that superthrive just add 1 or two capfulls per gallon - I usually do two actually for good measure, that will bring your PH down about 1 to 2 points - fox farm has oyster shells which act as a PH buffer to help stabilize your PH, using this method your PH should be fine.