Does your pH controller read too high or too low when it needs to be calibrated?

[whatcaneyedo]

I've been finding that after about 3 months my pH controller starts to read my tanks pH about .2 higher than if it was freshly calibrated. For instance, in the summer the tanks normal pH range is 7.9 to 8.1 So if after a while the controller starts reading it up around 8.3 I begin the question if the controller is lying to me and if I should re-calibrate the probes. Do the rest of you experience the same thing or does your pH reading go down in time?