Is my pH probe failing?

[Monkichi]

I noticed and interesting difference between 2 pH probes I have. One is fluctuating quite a bit and the other is much more smooth. Could the erratic one be failing?

Some context: Both probes are in my sump next to each other in the return pump section. I also drip my ATO in there pretty close to them which is why I added ATO to the graph to see if that made the pH reading dip. pH is a standard apex probe ~5yr old, pHx9 is a BRS lab grade probe ~2-3yr old; neither one has been calibrated in a few months. I was thinking about calibrating one of them and seeing what happens. Let me know what you guys think and if you need any more info. Thanks.

 

[Monkichi]

Sorry for double pic, I tried to edit the post to delete it, but I can't get rid of it.

 

[nautical_nathaniel]

I would try calibrating them and see if that helps.

 

[Monkichi]

I would try calibrating them and see if that helps.

You think I should just calibrate the wonky one and see or go ahead an calibrate both at the same time?

 

[nautical_nathaniel]

You think I should just calibrate the wonky one and see or go ahead an calibrate both at the same time?

I would honestly do both, I think you're supposed to calibrate them a couple of times a year anyways.

 

[Monkichi]

I have read that also. Another interesting observation is the older neptune brand one is always lower than the BRS lab grade one. Been that way for years. I guess I should use a test kit to see which one is closer to that.