Detect two points of reference for accurate pH monitoring. Use calibration solutions that are on either spectrum of the pH you intend to monitor. For aquaponic tanks where the pH is normally 7.8-8.5, use calibration solutions 7.0 and 10.01. For aquaponic systems where the pH is normally below 7.0, use 4.01 and 7.01 calibration solutions. 4.01 pH - The lower threshold reading your pH monitor or controller will require for use with calcium reactors for saltwater aquariums, solutions below 7.00 pH, and also most aquaponic systems. 7.01 pH - Neutral pH calibration packet. This is used by almost all pH monitors and controllers for calibration. 10.01 pH - The higher threshold reading your pH monitor or controller will require for use with saltwater aquariums or solutions above 7.00 pH Calibration packets can be stored in a cool dry area for up to 1 year.