Can't get my PH probe to read correctly while in tank. Any tips?

[AlexR]

Anyone have any tips to get a PH probe to read correctly?

I have the probe on a reef angel controller. I have calibrated numerous times using the 7 and 10 solutions.

The probe will not go above 7.5ph while in the refugium. If I put the probe in a glass with tank water, but out of the tank it reads correctly 8.1 to 8.3ph.

I have put in grounding probes in my refugium and DT just to be sure there is no stray voltage.

On top of this I have a salinity probe close to the PH probe and the salinity probe reads correctly while in the refugium.

I placed the PH probe in the same chamber as the return pump, this is the least turbulent chamber in my refugium and had no micro bubbles.

This is really driving me nuts...

Are there any tips anyone knows of?

 

[loudell]

This may be shocking to you but have you considered that it could actually be your pH?

You can put the probe into 2 different (fresh pouches) of calibration fluid to see if it reads them correctly and you can conclude if the calibration fluid is read correctly then your refugium reading is also correct...

 

[AlexR]

This may be shocking to you but have you considered that it could actually be your pH?



You can put the probe into 2 different (fresh pouches) of calibration fluid to see if it reads them correctly and you can conclude if the calibration fluid is read correctly then your refugium reading is also correct...

In my original post I said I tested the same water in a glass and it read above 8.0.
I have also ran multiple test kits and all cane above 8.0.
So no - it's not the correct readings.


Sent from my iPhone using Tapatalk

 

[loudell]

As you move that water sample from a (potentially sealed) refugium to a glass there is a good chance you are aerating it and degassing the CO2 which could be suppressing the reading to the low measurement you are seeing.
It is always best to measure pH in the tanke and not moving it to a glass or vial especially if it is going to be agitated or shaken prior to measurement.

 

[AlexR]

It's funny. I'm asking for some help if advice and I get someone trying to make me out to be stupid...

It may come to a shock to you that I test my PH in more then one way.

Somehow the probe reads incorrectly only when in my refugium.
I did try to explain everything in my original post.

I would really appreciate advice from anyone with experience with PH probes.

Thanks.

 

[AlexR]

As you move that water sample from a (potentially sealed) refugium to a glass there is a good chance you are aerating it and degassing the CO2 which could be suppressing the reading to the low measurement you are seeing.

It is always best to measure pH in the tanke and not moving it to a glass or vial especially if it is going to be agitated or shaken prior to measurement.

I test PH using the high range API test kit.
It reads closer to 8.3 based on the test kit.

I'm sure my PH is not that low.

 

[loudell]

Please don't misunderstand me. I never intended to make any disparaging remarks. I just wanted to allow for the possibility of thinking outside the box to a possibility that the probe could potentially be correct.

I do have a pretty good understanding of pH instrumentation and just wanted to be helpful.

 

[AlexR]

Please don't misunderstand me. I never intended to make any disparaging remarks. I just wanted to allow for the possibility of thinking outside the box to a possibility that the probe could potentially be correct.



I do have a pretty good understanding of pH instrumentation and just wanted to be helpful.

I'm sorry. It's easy to take things out of context. I'm just so frustrated with this thing.

 

[loudell]

pH is always best measured with a pH instrument referenced to high quality calibration fluids.

when you use the API Kit do you take the water sample out of the tank and shake it after the reagent is added? If so the sample is being actively degassed of CO2.

 

[AlexR]

Tomorrow I'm going to try and recalibrate it again.
It's also a brand new probe.

Just to be sure I leave the doors open for the refugium all the time to air out and also leave the window open not far from the tank. No change on the probe reading.

 

[AlexR]

pH is always best measured with a pH instrument referenced to high quality calibration fluids.

when you use the API Kit do you take the water sample out of the tank and shake it after the reagent is added? If so the sample is being actively degassed of CO2.

I believe that's how I do it. Is there another way?

 

[AlexR]

I'm also going to order another calibration fluid brand.
I've read some reviews saying the 7 calibration fluid was off.

 

[loudell]

IMO pH can not be accurately measured by taking the sample out of the tank and putting it into a vial with an airspace between the sample meniscus and vial cap only to be shaken. This will degass CO2 which has a strong impact on pH.
Obtain a good pH instrument with 2 point calibration a lab grade replaceable probe. Calibrate it and put into your system. If you see a suspicious reading just put the probe back into 2 different calibration fluids to see if it is indeed reading correctly or needs to be tweaked. Your pH instrument does not know how to read the calibration fluid correctly and be incorrect when it is in the refugium.

 

[AlexR]

IMO pH can not be accurately measured by taking the sample out of the tank and putting it into a vial with an airspace between the sample meniscus and vial cap only to be shaken. This will degass CO2 which has a strong impact on pH.
Obtain a good pH instrument with 2 point calibration a lab grade replaceable probe. Calibrate it and put into your system. If you see a suspicious reading just put the probe back into 2 different calibration fluids to see if it is indeed reading correctly or needs to be tweaked. Your pH instrument does not know how to read the calibration fluid correctly and be incorrect when it is in the refugium.

Are there not other factors?
Stray voltage? Micro bubbles? Vibration? Temperatures? Maybe others I don't know about?

 

[loudell]

The factors of Stray voltage, temperature differences, micro bubbles, vibration are quoted frequently but the chances of them accounting for a low reading are just about zero.
Micro bubbles are a remote possibility however they can be easily diagnosed. If you suspect micro bubbles just swirl the tip of the probe to remove them and note the reading. If it stays the same there were no micro bubbles.
I have seen on rare occasion AC line voltage to the pH meter device exhibit interference but it is always a constantly unchanging reading and not a steady 0.4 off.

 

[loudell]

Can you take a picture of your refugium or describe its contents and the location of the pH probe?

 

[AlexR]

The factors of Stray voltage, temperature differences, micro bubbles, vibration are quoted frequently but the chances of them accounting for a low reading are just about zero.
Micro bubbles are a remote possibility however they can be easily diagnosed. If you suspect micro bubbles just swirl the tip of the probe to remove them and note the reading. If it stays the same there were no micro bubbles.
I have seen on rare occasion AC line voltage to the pH meter device exhibit interference but it is always a constantly unchanging reading and not a steady 0.4 off.

Ok... let's say my PH is indeed this low.
I'm open to it.

What should I do to raise it?
Kalkwasser?

 

[wrott]

Do you use a Ca reactor?
And you did move the probe to all areas of the tank and still 7.5?
Usually interference will cause the reading to bounce around.

 

[AlexR]

Do you use a Ca reactor?
And you did move the probe to all areas of the tank and still 7.5?
Usually interference will cause the reading to bounce around.

I don't use a Ca reactor.
I've tried everything except putting the probe in the DT.

 

[loudell]

Is the refugium loaded with calerpa, etc? and is the probe close to the algae?