[ahem]

The API pH test from the master kit shows my evening pH (without Co2) as higher than what my new Milwaukee pH controller shows. I calibrated the controller before use and did a test in the 4.0 buffer last night (controller was dead on with the buffer). The pH meter was showing 7.2, yet my API kit showed closest color is 7.6, the nearest next color on the card is 7.2 which has green tint and my result had no green so the API kit was telling me it was at least 7.3 and probably closer to 7.6.

My wild hypothesis at the moment is that the API pH tests are less accurate at the ends of their ranges so a pH in the 7.2 to 7.6 range is not well measured by either of the API pH tests since the pH test ends at 7.6 and the pH High tests begins at 7.4

On the flip side, I've worked in labs and with hydroponics before and know that probes are not perfect. Which do you think are more trustworthy, a probe or API chems?

 

[pauld738]

I have a pinpoint monitor that calibrates to 7.0 and 4.0 solutions yet when placed in any of my tanks reads 0.3 lower than it should. Not sure what is going on with that.

And I switched probes. So it's definitely the unit. Not probes.

So yeah it could be the controller.

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[ahem]

I'm inclined to trust chemical tests more. The exception is when the pH to be measured is on the ends of the chemical test range, then not so sure.

Your pH controller experience there is concerning since I think PINPOINT is a reputable company. I think my approach will be to continue to use the pH controller as a quick check and back stop for CO2 (controller shuts off CO2 in case my bubble rate is off) and still continue the API tests 2x daily (also have a drop checker in there).

The other issue I notice (and remember from lab days), the pH controller/meters are slow. You have to give them time to settle.

 

[pauld738]

The other issue I notice (and remember from lab days), the pH controller/meters are slow. You have to give them time to settle.

Totally agree! I calibrate by walking away. Lol!

I actually trust pH probes more then chemical tests. You don't get the same pH picture using chemical tests. But I understand probe limitations. And use kh as an absolute test.

And to be clear. Those are pH monitors I am using not controllers. Don't know if they use the same circuit board.

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[Greggz]

I've tested a calibrated probe against the API liquid test, and in my opinion, the API is kind of a reasonable guess. Many times it is off quite a bit. At least to my eye, and that is part of the issue. Is that 7.6? or 7.4? or 7.8? Depends on how you perceive the color.

IMO, the deeper you get into the hobby, the more important precise control of CO2/pH drop becomes.

I drop mine in 0.05 increments until I hit the sweet spot. About once every six weeks I calibrate my American Pinpoint Marine probe, and it is rarely off more than 0.02. Very, very consistent. It also stays in the tank all the time. The biggest weakness of pH "pens" is how you store them between uses. You don't buy those probes, you rent them. They can go bad pretty quickly.

As usual, just my experience.....your mileage may vary.

 

[ahem]

I've tested a calibrated probe against the API liquid test, and in my opinion, the API is kind of a reasonable guess. Many times it is off quite a bit. At least to my eye, and that is part of the issue. Is that 7.6? or 7.4? or 7.8? Depends on how you perceive the color.

That is very true. I have a light in the area where the tank is that has a cold white light and I find I need that harsh white to properly see the colors. Sometimes I pass the vial over the color card to see which color is LEAST visible through the vial (although that does not work with a dark solution). It's easier when you are on the boundary of a two color mix, less so when it is just a shade darker or lighter. For example the API phosphate kit is near impossible to tell between the three shades of green between 0 and < 1ppm. However the pH kit has blue only for 7.6 with green mixing in as you go to 7.2 and lower. So it's easy to see that it is pure blue or has a greenish tint. Same with the ammonia test, any greenish tint deviating from pure yellow means some ammonia.

 

[Darkblade48]

I'd say both have their pros and cons, and if I had to choose, I would say use one, but verify with the other

pH probes should be calibrated on a regular basis, using at least a 2 point calibration (ideally 3 point). They also have to be stored properly in a 3M solution of potassium chloride when not in use. If you just keep them immersed in aquarium water, they will eventually go bad, so you also have to keep that in mind.

As for chemical tests, they're a bit less finicky in terms of storage, but human error plays a large role (as already mentioned). You probably could make it more quantifiable with a spectrophotometer, but there's really no such need for accuracy in our hobby

 

[en7jos]

I bought a new HM Digital pH pen (new model, seemed best accuracy available, temp compensated, etc) and did 2-point calibration. To be honest it's next to useless in my tank so I've gone back to my API chemical testing. Not sure if this is because of 0KH, but it takes so long to settle that usually turns itself off before reading looks even half sensible. Put it back into cal solution and the readings are on the dot, straight away. I can assume that it just doesn't play well in 0KH water. The API test at least seems consistent, but you do have to accept at least a +/- 0.2pH uncertainty from my experience.

Does anyone know if API chemical tests are affected by 0KH, and if so, in what way please?

 

[pauld738]

I bought a new HM Digital pH pen (new model, seemed best accuracy available, temp compensated, etc) and did 2-point calibration. To be honest it's next to useless in my tank so I've gone back to my API chemical testing. Not sure if this is because of 0KH, but it takes so long to settle that usually turns itself off before reading looks even half sensible. Put it back into cal solution and the readings are on the dot, straight away. I can assume that it just doesn't play well in 0KH water. The API test at least seems consistent, but you do have to accept at least a +/- 0.2pH uncertainty from my experience.



Does anyone know if API chemical tests are affected by 0KH, and if so, in what way please?

Yeah, pH probes need a certain amount of carbonates to get a reading.

The limited amount of reading I have done on chemical tests suggest they are not affected by the lack of Kh.

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[en7jos]

Thanks Paul. So I guess API liquid tests could be considered more accurate than an electronic probe / pen device then when you're dealing with 0KH conditions then?

 

[pauld738]

For sure the probes can't handle it. In true 0kh water.
I do suspect it doesn't take much though. But that is just my very unscientific perception of what is happening when I have used pH probes in very low, but not true 0kh water.

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[Greggz]

pH probes should be calibrated on a regular basis, using at least a 2 point calibration (ideally 3 point). They also have to be stored properly in a 3M solution of potassium chloride when not in use. If you just keep them immersed in aquarium water, they will eventually go bad, so you also have to keep that in mind.

I can only speak to my experience.

My American Pinpoint Marine probe has stayed in my tank for about 3 years.

I calibrate once every six weeks or so.

Rarely off more than 0.02.

I'm actually amazed at how well it stays in calibration.

Bump:

Yeah, pH probes need a certain amount of carbonates to get a reading.

I would say it's very little.

My water is about 1 KH.

pH probe works great rock solid and consistent.

But IMO it does pay to get quality probe.

Cheap ones don't last long.

 

[pauld738]

I can only speak to my experience.



My American Pinpoint Marine probe has stayed in my tank for about 3 years.



I calibrate once every six weeks or so.



Rarely off more than 0.02.



I'm actually amazed at how well it stays in calibration.

I've seen you say that before. And it does seem odd, especially with my experience. Not saying that it's wrong though.

I didn't think the Pinpoint probes that come with the unit were gel filled. Maybe that helps. I have noticed my gel filled probe holder longer than any of the Pinpoint probes I've ever received.

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[Greggz]

I've seen you say that before. And it does seem odd, especially with my experience. Not saying that it's wrong though.

I didn't think the Pinpoint probes that come with the unit were gel filled. Maybe that helps. I have noticed my gel filled probe holder longer than any of the Pinpoint probes I've ever received.

Yeah mine is a small sample size......just one.

And maybe I am lucky.

But I will say I bought cheap probes and pH pens and most are pretty much junk. Very unreliable and prone to failure.

 

[ahem]

I have an APERA pH pen arriving today that I hope is better than the $20 Chinese pens. I want to check against my Milwaukee controller and have some to use in buckets etc..

My experience from hydroponics and in lab was that removing the probe from a solution was the main death sentence. Even when you store it properly it is a challenge to keep the probe effective and not drifting. I think leaving in tank works to extend the life.

As far as the chemical tests like API, there seem to be fewer variables. If you make/count the drops properly and are using a clean tube and fresh reagents, it's going to reliably produce the same result each time, every time. There is more behind the scenes with a pH meter: probe health, unit calibration, unit software/firmware, the kh content of what you are testing ...

 

[pauld738]

I have an APERA pH pen arriving today that I hope is better than the $20 Chinese pens. I want to check against my Milwaukee controller and have some to use in buckets etc..



My experience from hydroponics and in lab was that removing the probe from a solution was the main death sentence. Even when you store it properly it is a challenge to keep the probe effective and not drifting. I think leaving in tank works to extend the life.



As far as the chemical tests like API, there seem to be fewer variables. If you make/count the drops properly and are using a clean tube and fresh reagents, it's going to reliably produce the same result each time, every time. There is more behind the scenes with a pH meter: probe health, unit calibration, unit software/firmware, the kh content of what you are testing ...

I'm going to play the devil's advocate here and say that there are just as many variables. And a liquid test is not going to give you the same pH picture of your tank that a monitor (not pH pen) will give you.

Are you testing with a liquid test kit every minute, or 10 minutes, hour, etc? Are you testing when you put in Ferts, at midnight or 4am? Is your water sample representative of the entire tank (surface water or mid column)? And reagents do come in doa from time to time.

With only a snapshot, a liquid test kit (pH pen too) can give the wrong impression of what's happening in the tank.

That said, I do understand what you are saying.

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[Greggz]

I'm going to play the devil's advocate here and say that there are just as many variables. And a liquid test is not going to give you the same pH picture of your tank that a monitor (not pH pen) will give you.

Agreed.

Even the age of the API kit can make a difference. I have tested samples side by side with two bottles and got different readings.

And much of this discussion depends on your goals.

IMO, managing a high light high tech tank with API drops would be a nightmare. You would have to be testing constantly to understand what is going on in the tank. And CO2 is too important not to get it right.

If low tech and just curious about pH, anything will do as absolute reading means little.

Also agree that a monitor is much better than a pen. A snapshot a couple of times a day is different than being able to glance at any time and see where you are.

Even today if I see something wonky in my tank, the first thing I do is double and triple check CO2 and pH drop. If it isn't right, all the other adjustments probably won't save you. And if you get it right, everything else is easier (Geez I am sounding like Tom Barr now!).

 

[ahem]

I have a pinpoint monitor that calibrates to 7.0 and 4.0 solutions yet when placed in any of my tanks reads 0.3 lower than it should. Not sure what is going on with that.

And I switched probes. So it's definitely the unit. Not probes.

So yeah it could be the controller.

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I wonder if the .3 difference is firmware related. If you own both of those and they have a firmware, which they would have something, you might want to check they are on the same version. The pH number we see is the result of probably many calculations in unit, so I can see where they might "tune" their calculations in a newer firmware release.

 

[ahem]

IMO, managing a high light high tech tank with API drops would be a nightmare. You would have to be testing constantly to understand what is going on in the tank. And CO2 is too important not to get it right.

It's not a nightmare but it does take a lot of time. I can see a model of using both liquid and meters, of course I only have one 50g tank (in process of moving stock from 20g). So maybe if I had a bunch of tanks it would quickly overwhelm.

I can see reducing these tests as I get more comfortable but am doing this mix of electronic and chem tests for the forseeable future. I have a bunch of pH tests because I don't completely trust any of them yet. In totals 13 chemical tests per day and 6 tests using electronic equipment.

3am (I go to bed late so this is in prep of the next day, also when I dose nutrients and excel, all tests prior to nutrient addition, except TDS which is before and after)
- Milwaukee pH monitor check
- APERA pH meter check
- API pH high test
- API pH low test

- TDS meter check for TDS PPM x2 (use to compare to API GH test), I check this before and after nutrients addition
- API GH test
- API KH test

- API Ammonia test
- API Nitrite test
- API Nitrate test
- API Phosphate test
- Hanna Checker HC Iron test (new)

12pm noon (day check also when I dose "bacteria in a bottle")
- Milwaukee pH monitor check
- APERA pH meter check
- API pH high
- API pH low

- API Ammonia test
- API Nitrite test

throughout day, drop checker, temp, and Milwaukee pH checks.

so I guess I am "constantly testing" though.

 

[Greggz]

It's not a nightmare but it does take a lot of time.

LOL I think you just laid out a "nightmare" for me.:grin2:

Boy, that is a LOT of testing.

Is this tank cycling? Just curious why so many ammonia, nitrite, nitrate, phosphate tests?

And why KH/GH daily? Do you they change much at all? If you know KH, you can make a reasonable assumption of degassed pH. So you should be able to tell if your reading is in the right ballpark. Does your KH change often?


And precise GH level is not very important in the scheme of things. Enough but not too much. Anywhere from 4 dGH to 8 dGH for most tanks.

As to multiple pH tests, to me the absolute value is not that important. It's a consistent relative measurement that counts. For instance, my degassed pH is 6.4. Now whether that is really 6.3 or 6.5 makes little difference. What does matter is a consistent relative pH drop.

And IMO, the best most consistent relative pH reading is from a good calibrated probe left in the tank at all times.

But as always, whatever works it good by me.