Can't calibrate two month old pH probe

[vessxpress1]

I bought my Neptune Apex a couple months ago and it came with the new temp and pH probes. The first month was great. Then the pH probe seemed to start reading low. Now about 2 months later you can't even calibrate it. It's not dirty. I tried calibrating it a few times here today and when I was done it was reading worse than when I started. I tested my pH with a hannah tester and the probe in the tank is reading 0.3 to 0.4 low. This is after calibration.

 

[Neoalchemist]

Sometimes they suffer from electrical interference. Try isolating the wire from the rest of the power cords. Also make sure you dont have an unusual amount of stray voltage in the water. You can isolate the wire and take a sample out of the tank and test it in a separate container to see if something else in the tank is causing interference.

 

[Neoalchemist]

Ive also had a controller that suffered from electrical feedback and was never able to properly calibrate ph. So I manually adjusted the reading so it was more in line with a hand held unit and left it that way. It was accurate enough to run my calcium reactor but I used a backup for my accurate ph checks.

 

[vessxpress1]

Thanks for the tips. I do actually have the pH probe wire tied to all my other power wires. I'll try that. I have a grounding probe on the tank that is plugged directly into a grounded GFCI. Neptune got back to me in less than 24 hrs. Gave me some steps to run though for a manual calibration. I ordered some more pH fluid as I'm worried that some of my packets may be getting contaminated. My hannah checker seems to be reading more reasonably. Going to check some packets with it now.

 

[vessxpress1]

Ok, I think it's back. First I got the wire isolated then I tested the packets with Hanna meter to see which was the closest. Had a 7 that was reading 0.02 higher than it should and a 10 within 0.05. Ran manual calibration with those and went from reading 7.75 in the tank to 8.00. Which is where the Hanna is reading. I might have been calibrating off of a bad packet. I got rid of a couple. Have new bottles of solution coming.

pH is running low as the house is sealed up with two central air units running. Have an air line from outside going to skimmer but it doesn't seem to be helping much.

 

[Neoalchemist]

I have the opposite problem because I top off with kalk. Also we dont run ac.

 

[vessxpress1]

I have the opposite problem because I top off with kalk. Also we dont run ac.

I want to top off with kalk but I don't think I can yet. I don't have enough demand and I'm afraid it'd be too much after a while. I've got a GEO kalk reactor on the floor ready to go.

 

[vetteguy53081]

Likely pucked up elements such as alk, calcium, etc. Rinse in RO WATER then calibrate agat

 

[Neoalchemist]

I want to top off with kalk but I don't think I can yet. I don't have enough demand and I'm afraid it'd be too much after a while. I've got a GEO kalk reactor on the floor ready to go.

With a kalk reactor it is kind of all or nothing. I gravity topoff kalk. So I could just adjust the concentration to suit the tank needs. Until the topoff water can hold no more kalk then plans have to change.
One thing you can do is use a ph controller to stop the kalk addition at 8.5 but this only works if you run a separate fresh water top off to step in when the controller has the kalk topoff suspended.
In a moderate sized tank, sps or mixed reef you can get by for years with no additions other than kalk and an occasional magnesium dose.