3 pH probes, 3 calibrations, 3 (way off readings)

[BPiers]

Hi everyone.
Having an issue with pH probes. I have two permanently installed in the tank. All are Lab Grade Probes. All calibrated with fresh 10.0 and 7.0 after temp adjusting the fluid in the tank. KH 9.3, Cal 446 (both Hanna)

After calibration, my main pH reads 7.57. My other probe is brand new, BRS Lab grade, also calibrated with the same solution at the same time. It reads 7.65
I pulled my CaRx probe and dropped it in the sump for a quick check - it reads 8.13. I don't have any 4.0 fluid to calibrate with. Should I calibrate it with 7/10 for a third check??

Confirmation after calibrating both probes in the fluid is spot on 7.0 and 10.0.

What is going on here??!!

Everything in the tank looks great.

 

[Bob Escher]

I had the same problem my probes were off my probes were reading in the 7.55, to 7.67 after I calibrated them with fresh, 4 0 and 7.0 fluid. I finally bought a Hanna PH checker and after calibrating twice my readings were at 8.25. Much different, I'm relying on my Hanna from now on and take the other readings into consideration

 

[BPiers]

Yeah, but with a $$$ Apex and Lab grade probes, that shouldn't be necessary (at all!)
I just recalibrate my CaRx pH probe (pH in the tank is more important IMO), and its 7.57. Ok...so now I find I have low pH (noticed it the other day and turned the CO2 off and the CaRx is off also, so no low pH effluent is going into the tank..
I've been dosing Alkalinity to get the pH up, but it falls so fast. Same with Kalk in my top off water. pH drops very fast. Over the past week I have done a total of 55 gallon water change in a 93 cube.

 

[n2585722]

Are these brand new probes? If so give them a week in the tank and recalibrate them. Also it may be the CO2 content of the air in your house. I noticed when the 5 grandkids stay the night my pH drops like a rock too about the levels you are seeing.

 

[nicholas.babb@gmail]

I learned not to use ph probes. They cause more confusion than anything. Even 7.57 to 7.67 is enough of a difference to drive me crazy. Monitor and stabilize alkalinity and your ph should be ok.

 

[BPiers]

I ordered new calibration fluid, hoping it was a bad batch, but the fluid reads 7 and 10 on the nose.
I even picked up a BRS CO2 scrubber thinking that was going to help...7.4 this am. All looks okay in the tank.

 

[BPiers]

Just to close the loop - I got my new calibration fluid and I calibrated the probes 3x, each with a much better reading.
I didn't think I needed to calibrate, and recalibrate, and recalibrate, but I don't suppose theres any harm in doing it, is there? My apex graphs now are very very stable.