What ph number to believe

[Lionfish hunter]

I have tested ph hundreds of times with many different tests. and have absolutely no idea what it actually is. My api test shows 7.7-8.1, a Hanna checker which I threw away showed anywhere from 7.8 to flashing 8.6 on the same day depending on what bottle of reagent I used. I even bought the Hanna calibrated ph vials to make sure the checker was working properly as recommended by hannah, it was. My Hanna ph probe calibrated with 2 different fluids shows 7.6-8.0. Seneye generally shows 8.2-8.35. And now I have a brand new GHL calibrated probe connected to my profolux controller showing 8.35-8.45 which also seems impossible. See attached.

My alkalinity stays at 8.5. I only dose all for reef. I have an appropriately sized skimmer. A large refrugium with a mountain of chaeto that runs 12 hours at night under a very bright grow light. And there are very little people in my house breathing co2. 3 radios G5’s at 50% over a 235 gallon tank. If nobody is in the house for days, my ph numbers do not change. I have 2 mp40s as high as they can go toward the surface at 100% on reef crest.

If I take a cup of water out and put an air stone in it, inside the house, the ph will boost from 7.8 to 8.2 according to api, which oddly enough I trust the most even after spending hundreds on other tests. And I’m not sure how I don’t have enough airation.


I seriously have no idea what my ph actually is.

@Randy Holmes-Farley any input?

 

[taricha]

My api test shows 7.7-8.1, .... My Hanna ph probe calibrated with 2 different fluids shows 7.6-8.0.

Sounds like these two are telling you the same story.

 

[Uncle99]

Maybe none are actually correct.
I use the API for PH, not overly concerned of PH

 

[Lionfish hunter]

Sounds like these two are telling you the same story.

Yes but my calibrated GHL probe and seneye also give the same number that is drastically different.

 

[Lionfish hunter]

Maybe none are actually correct.
I use the API for PH, not overly concerned of PH

It is astonishing how bad aquarium test kits are. Nitrate test kits seem wildly inaccurate as well.

 

[Randy Holmes-Farley]

To try to sort out what is accurate and what is not, this is what I would do.

Buy new, brand name pH calibration buffers, typically pH 7 and 10.

Allow the fluids to come close to tank temperature (pH measurement is temp dependent, and while some devices correct for this effect, they may not do it correctly, the effect may be turned off, etc.). FWIW, pH buffers also have a temperature dependence, which is different than the measurement effect, although not all may indicate this to you. For example:

https://www.labchem.com/media/buffer-temperature-profile.pdf

Calibrate each device using these same fluids. Check to be sure the devices accurately measure the calibration fluids after calibration (to within your level of needed accuracy).

Then measure the same seawater at the same temperature using these devices and see what you find. This will also be the first step where you can use the pH kit since most do not have the range to read the calibration buffers.

Measuring pH in a cup out of the tank may be best to determine if there are electrical issues such as a ground loop problem (tank should read same as cup, and if it doesn't, there's a problem to solve).

 

[Lionfish hunter]

To try to sort out what is accurate and what is not, this is what I would do.

Buy new, brand name pH calibration buffers, typically pH 7 and 10.

Allow the fluids to come close to tank temperature (pH measurement is temp dependent, and while some devices correct for this effect, they may not do it correctly, the effect may be turned off, etc.). FWIW, pH buffers also have a temperature dependence, which is different than the measurement effect, although not all may indicate this to you. For example:

https://www.labchem.com/media/buffer-temperature-profile.pdf

Calibrate each device using these same fluids. Check to be sure the devices accurately measure the calibration fluids after calibration (to within your level of needed accuracy).

Then measure the same seawater at the same temperature using these devices and see what you find. This will also be the first step where you can use the pH kit since most do not have the range to read the calibration buffers.

Measuring pH in a cup out of the tank may be best to determine if there are electrical issues such as a ground loop problem (tank should read same as cup, and if it doesn't, there's a problem to solve).

Okay I will try that, thanks.

 

[Uncle99]

It is astonishing how bad aquarium test kits are. Nitrate test kits seem wildly inaccurate as well.

Yup, different kits produce different results.
What I find useful is when a single kit measures consistently and when those results “make sense”.

While you can run stuff high or low it’s the stability of the results which count IMM, fluctuating levels are not what we want.

Calibrated probes worked well initially, but after some time, produced “unbelievable” results.

So I stuck with API for PH only, it’s says 8.2 always at the same time of day, so I just except that.

 

[Lionfish hunter]

To try to sort out what is accurate and what is not, this is what I would do.

Buy new, brand name pH calibration buffers, typically pH 7 and 10.

Allow the fluids to come close to tank temperature (pH measurement is temp dependent, and while some devices correct for this effect, they may not do it correctly, the effect may be turned off, etc.). FWIW, pH buffers also have a temperature dependence, which is different than the measurement effect, although not all may indicate this to you. For example:

https://www.labchem.com/media/buffer-temperature-profile.pdf

Calibrate each device using these same fluids. Check to be sure the devices accurately measure the calibration fluids after calibration (to within your level of needed accuracy).

Then measure the same seawater at the same temperature using these devices and see what you find. This will also be the first step where you can use the pH kit since most do not have the range to read the calibration buffers.

Measuring pH in a cup out of the tank may be best to determine if there are electrical issues such as a ground loop problem (tank should read same as cup, and if it doesn't, there's a problem to solve).

Calibrated the Hannah and the GHL probe. Put them both in the same 7.00 ph solution afterwards and the GHL read 6.98, Hannah 6.74 (see image) Both in the same solution, both calibrated 1 min before. This will be 200$ in Hannah ph testers that will be in the trash. The GHL is now reading 8.07 now, down from 8.35 after this calibration. which is similar to api.
Why is Hanna adverted and basically touted by many to be the best? I have 2 differed ph testers, nitrate, phosphate, copper, and alk checkers. You know how the ph testers have worked out for me. The nitrate checker is completely worthless(so was nyos, the only consistent one I have is api which costs like 6$) and the phosphate reagent has a solid chance of being really bad too. Their alk testers is fantastic but that is it. Copper one will give you better results compared to any others but I’ve found it is not that accurate either. Never heard anybody else talk about this. Does everybody just assume their numbers are right because it’s Hannah? I have done extensive testing especially with nitrate and the results are very sad.

 

[Randy Holmes-Farley]

Reefers do have a tendency to believe their tests are accurate when they may not be. I’ve never used a Hanna pH device myself.

 

[Lionfish hunter]

Reefers do have a tendency to believe their tests are accurate when they may not be. I’ve never used a Hanna pH device myself.

I now have a GHL profilux ph probe and a Neptune apex ph probe. And I am no closer to knowing what my actual ph is. Both are calibrated and confirmed to read correctly in their calibration fluid. But in the aquarium they are almost .3 different! How can this be? If they both read the same in calibration fluid, how can they be that far off?

I have attached screenshots of the Neptune ph in calibration fluids 7 and 10 fluids and in the tank ph reading 7.95. Also screen shots of the GHL ph probe in calibration 7 and 9 fluids and the tank ph reading 8.21. I let the probes sit in their calibration fluid for 10 min before taking screen shots to ensure the probes were at the correct level.

 

[Lionfish hunter]

And the temps are 2 degrees off too. Almost 2000$ worth of equipment and they do not read anywhere close to each other on anything. Ghl probe is 2 months old, calibrated 3 times but has always read consistent. Apex probe is 3 days old. I have calibrated in 6 times and it drastically changes each time. Finally got it reading the calibration fluids correctly after calibration this last time.

 

[Lionfish hunter]

I run a recirculating co2 skimmer and dose 1 gallon of kalk per day. 235 gallon aquarium.

 

[arking_mark]

Thread 'A simple way to assess your pH measurements' https://www.reef2reef.com/threads/a-simple-way-to-assess-your-ph-measurements.963037/

 

[fishmonkey]

I would trust a well calibrated probe over and test kit for ph. I can’t read those things for the life of me.

 

[gbroadbridge]

I now have a GHL profilux ph probe and a Neptune apex ph probe. And I am no closer to knowing what my actual ph is. Both are calibrated and confirmed to read correctly in their calibration fluid. But in the aquarium they are almost .3 different! How can this be? If they both read the same in calibration fluid, how can they be that far off?

I have attached screenshots of the Neptune ph in calibration fluids 7 and 10 fluids and in the tank ph reading 7.95. Also screen shots of the GHL ph probe in calibration 7 and 9 fluids and the tank ph reading 8.21. I let the probes sit in their calibration fluid for 10 min before taking screen shots to ensure the probes were at the correct level.

Sample of tank water in a bucket.

Measure pH of the sample with the Apex and the GHL individually - not in the bucket at the same time.

Make sure the relevant temp probe is in the bucket too

 

[arking_mark]

They are both potentially right. These probes have an accuracy of +/- 0.2.

7.95 +/- 0.2 has overlap with 8.2 +/- 0.2. So if your actual pH is in the overlap, they both are right!

 

[Dennis Cartier]

And the temps are 2 degrees off too. Almost 2000$ worth of equipment and they do not read anywhere close to each other on anything. Ghl probe is 2 months old, calibrated 3 times but has always read consistent. Apex probe is 3 days old. I have calibrated in 6 times and it drastically changes each time. Finally got it reading the calibration fluids correctly after calibration this last time.

For the temperature part of the conflicting readings, get yourself a Tropic Marin High Precision Thermometer and you will know for sure what the exact temperature is, and which device needs calibration.

Whenever I have a conflicting reading between my Inkbird temperature controller, Thermo Scientific EC meter and Atlas Scientific temperature probes, I use my TM HP thermometer to figure out who is telling the truth.

 

[Randy Holmes-Farley]

I now have a GHL profilux ph probe and a Neptune apex ph probe. And I am no closer to knowing what my actual ph is. Both are calibrated and confirmed to read correctly in their calibration fluid. But in the aquarium they are almost .3 different! How can this be? If they both read the same in calibration fluid, how can they be that far off?

Aside from temp effects, you also used different calibration fluids. If one or more of those are off (and they can be), then that could explain it.

Do you have to use those specific pH values (7 and 10 vs 7 and 9) for calibration of these devices, or do you have a choice?

 

[Lionfish hunter]

Aside from temp effects, you also used different calibration fluids. If one or more of those are off (and they can be), then that could explain it.

Do you have to use those specific pH values (7 and 10 vs 7 and 9) for calibration of these devices, or do you have a choice?

I was able to calibrate the ghl with 7 and 10. It did move the ghl down .1 but still a .18 difference between the 2. Still not pleased and don’t know what to believe.