This is doing my head in: ph and test meters

[Lynnzer]

I'm just about to throw my arms up in frustration. I had a ph test meter that I'd forgotten all about from my freshwater days and have been using the API marine test kit. I just hate the ambiguity of trying to decide which colour is the nearest to the one with the liquid in the tube. It's a best guess situation only and I don't have faith in it providing a true ph reading.
So I ordered another ph test meter. In the meantime I found the one I had while searching through my spares bin.
I waited until the one I ordered arrived so I could calibrate them both with the included packets of 4.01 and 6.86.
Easy enough? Like hell it is.
I do the calibration exactly the same on both instruments and they never agree with each other.
I do a calibration with one of them and set the 6.86 and 4.01 when the readings settle. Then a few minutes later when I turn it back on the same test liquid results show differences to what the stick was calibrated to.
The second, ie the old stick, doesn't differ too much from the calibrated 4.01 and 6.86; perhaps an occasional 0.01 difference. The test liquids are tested again for the actual ph rather than calibration, and show the correct measure.
Now, when I test the reef tank one of the sticks, the new one, shows a reading of 7.43 and the old stick shows 9.18.
The API test solution is showing at 7.4ish.
I'm striving to get to 8.1 for the corals.
When I 1st tested the water without the sticks with only the API kit the ph was showing around 7.6ish.
As a consequence I raised the level slowly using bicarb of soda and ended up at around 8.3. I settled on that as being near enough to not matter much.
However when the new testing stick arrived it showed the water at 9.87. CHRIST ....... Panic.
So once again I made adjustments slowly using distilled white malt vinegar. But I'm at the stage where I really don't know what to trust to show the true ph.
The new stick shows 7.43 at present and the API kit shows more or less the same. I guess I should use the new stick based on the similarity or results, but as mentioned, the new calibration on it doesn't agree after calibration to the results given on an actual test dip in the test solution. It's the old stick that shows the 4.01 and 6.86 results immediately after calibration yet this is the one that is way out in the comparison to the API colour result. So the 9.18 reading now just throws me into despair. Old or new, or just go with the API kit?
What a bloody nightmare.
Surely there has to be an instrument that doesn't need a second mortgage to buy, which is as accurate as possible.
Any ideas guys and gals?

 

[taricha]

I would definitely not make any corrective actions directly for pH based on meters performing inconsistently.

Measure Alk, and keep alk where you want it. If you think the pH is too low - then have skimmer pull in outside air.

(pH meter calibration is a headache for me too. Only way I know to do it is to have 2-point calibration standards + more buffers of other known values, and after the two point calibration evaluate the meter on those other known buffers. )

 

[Reefer Matt]

Ph probes and meters usually have to stay wet to stay calibrated. Also, calibrate your meter or probe at 7 and 10, not at 4 and 7. You want to calibrate the probe for the range you are using. The 4.01 packets are for freshwater calibration. Also, I suggest a Pinpoint ph meter and probe. Usually around $100 US.

American Marine PINPOINT pH Monitor + Calibration Fluids https://a.co/d/9w0nRji

 

[jda]

If you want to worry about pH, then get a digital pH pen from Amazon or somewhere. Get a lot of calibration fluid and keep it calibrated. These pens are made to use sparingly and on demand and do not need to stay wet all of the time.

Also, get an indoor co2 meter. There are many for $40-75 that are fine. Inkbird makes one as do many others.

You will see a trend that as the co2 in your home rises, the tank pH will lower. it is easy to fix. Open a few windows and put a fan into one of them.

An alternative to looking at pH is to keep alk stable and forget that pH is a thing.

 

[exnisstech]

An alternative to looking at pH is to keep alk stable and forget that pH is a thing

This is exactly what I do. I can't remember the last time I checked pH. Probably when the tank wasn't doing well and I was ruling out possible causes.

 

[jda]

I will also add that higher co2 in homes can be a danger to humans and other pets, as well. Fresh air is good for everything. Some people are surprised at how much co2 that they have... and also how much better they feel and sleep once they replace some air. A member sent me a PM and had co2 about thrice the recommended level in their home and he was shocked at how his headaches went away when he got fresh air in... like instantly.

 

[Lynnzer]

I've sort of sussed it now. The new meter pen has been checked at the LFS against the results from a NT Labs test kit. The comparison was virtually the same depending on how the test liquid colour was shown against the colour chart.
Then I went and did a check of the water in the frag tanks and a couple of running show tanks that gave more or less the same reading as expected.
I also took some water from the frag tank home with me and used it on the old test meter which showed a level of almost 2.5 higher that what I know it to be.
Having had a good discussion on ph and the problems at the LFS, I was pointed to the KH being equally if not more important.
So I bought a Salifert test kit and the result on my main tank gives me a reading of around 12.9.
Is that too high? I believe that corals prefer a higher KH but how about the impact on fish? Would it not be better to go midway to the recommended levels for fish and coral at, say, something like a reading of 10? And if a compromise has to be made between ph and KH which would be the best track to go with?

 

[Lynnzer]

Did another Salifert test today after watching a "how to do it properly" clip on Youtube.
The KH reading is at 11.8. The ph is showing at 7.85.
Are these OK to work with?