Ph monitor
If you purchased entire set you should have bottles of calibration fluid. You need only small amount for actual calibration. As long as you have probe underwater, you will get accurate reading. Once you done with calibration you should discard used fluid.
I initially calibrated my controller in May and did it again last week. It was off only by .2
I initially calibrated my controller in May and did it again last week. It was off only by .2