− Decrease quantity for Bluelab PROBPH pH Probe for Water, Replacement Electrode for Meter, Monitor, and Controller with Easy Calibration, Tool for Hydroponic System and Indoor Plant Grow Quantity + Increase quantity for Bluelab PROBPH pH Probe for Water, Replacement Electrode for Meter, Monitor, and Controller with Easy Calibration, Tool for Hydroponic System and Indoor Plant Grow Add to cart