Don't bother with lab grade PH probes, not worth the extra $ IME, they are more for pressure rated installations.
You need 7.0 calibration fluide as your center point during calibration, the 10.0 is used if you plan to measure Ph value between 7 and 10, the 4 is used when measuring between 4 to 7. I don't think Neptune's combo packages comes with calibration fluide packs.
You need 7.0 calibration fluide as your center point during calibration, the 10.0 is used if you plan to measure Ph value between 7 and 10, the 4 is used when measuring between 4 to 7. I don't think Neptune's combo packages comes with calibration fluide packs.