What ph number to believe

arking_mark

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I have basically done everything you did here. Skimmer with a recirculating co2 scrubber, large refugium opposite my lights, and I know have a 55 gallon tank full of kalk dripping as much as I can to match evaporation.

I am not overly concerned with it, but my ph is not stable like yours. Around a .26 daily difference.

So there are several factors that contribute to CO2 levels in the tank and I can't quite control all of them. As my photosynthetic organisms have grown, my daily pH rise has also increased, and I've mostly given up controlling the highs. I would need fairly high (600+) indoor air CO2 and probably an even larger skimmer to compensate with.

My typical swings are now roughly between 8.18 and 8.28 with my setup and natural home CO2 levels. The 2 big factors are kids are now in college and household is half the size (6 to 3) and my house has lower CO2 in the colder and milder months. It's hard to drive down pH when my indoor CO2 levels have been mostly below 500ppm.

Natural reefs have something less than a 0.1 Total pH swing.

Post in thread 'Alkalinity stability? pH stability? Are they even different?' https://www.reef2reef.com/threads/a...y-are-they-even-different.711768/post-9382573

In terms of coral growth, I agree that elevated pH is great...BRS has some good evidence of this. However, I now have things that are growing too fast. As I'm not a coral farmer and I plan on keeping my tank for at least 8 more years...speed of growth isn't really desired.
 
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this is the basic specs of a low end lab grade mettler toledo s400 "specs" this is a benchtop unit.. by lab standards its about as cheap as you can get and still have a "real " piece of ph reading equipment for the work we do at our faciliy.
this is something you would find in a decent college chemistry lab.

notice how they use MV range, resolution and with the right probe it can read out to 3 decimal places. and its quite accurate... none of this "accuracy " is listed for any of the apex, ghl , hydros that i can find easily online.

see the difference ...


Temperature accuracy
pH-range-2.000 to 20.000
pH-resolutionSelectable 0.1, 0.01, 0.001
pH-relative accuracy±0.002
mV-range-2000 to 2000
mV-resolutionselectable 0.1/1
mV-relative accuracy±0.1
Temperature Range-30.0 to 130.0 °C
Temperature resolution0.1°C
According to earlier posts the GHL is +\-.1. The issue here is bean animal is saying that is a rounded number because of temperature and rounding of the probe to .1 decimal points actually means it is only accurate to +-.2
 
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So there are several factors that contribute to CO2 levels in the tank and I can't quite control all of them. As my photosynthetic organisms have grown, my daily pH rise has also increased, and I've mostly given up controlling the highs. I would need fairly high (600+) indoor air CO2 and probably an even larger skimmer to compensate with.

My typical swings are now roughly between 8.18 and 8.28 with my setup and natural home CO2 levels. The 2 big factors are kids are now in college and household is half the size (6 to 3) and my house has lower CO2 in the colder and milder months. It's hard to drive down pH when my indoor CO2 levels have been mostly below 500ppm.

Natural reefs have something less than a 0.1 Total pH swing.

Post in thread 'Alkalinity stability? pH stability? Are they even different?' https://www.reef2reef.com/threads/a...y-are-they-even-different.711768/post-9382573

In terms of coral growth, I agree that elevated pH is great...BRS has some good evidence of this. However, I now have things that are growing too fast. As I'm not a coral farmer and I plan on keeping my tank for at least 8 more years...speed of growth isn't really desired.
Well if you believe the people I have been arguing with. That high you have of 8.28 could mean anything from 8.08 to 8.48! Although you have it to 2 decimal points so not the same probe.

yes I have observed much more alkalinity usage when I am away at work and my ph goes up .2 compared to when I get home. Just this last week it went from 110 ml of all for reef and a gallon of kalk per day to 80 ml of all for reef and a gallon of kalk. In just 7 days after I got home after being gone for a week.

And it is potentially not just growth but health in higher ph. It has been observed that corals are more brittle and less able to survive stress events with lower ph.
 

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So to clarify, because this is what is being discussed. You believe the GHL has a manufacturer error of +\-.2? Meaning it is within its limits read either 7.9 or 8.3. Because I think GHL would have a big problem with that. And we are arguing about what their limits are.

Not to burst your bubble, but at BEST, these are +/- 0.1 accuracy. In practice, they are worse and I wouldn't expect better than +/- 0.2.

 

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to the point that the reef keeping devices are not accurate enought , not accurate enough for what?

in my reef i use ph probe in the calcium reactor (and i dont care if its 6.2 or 6.4 or 6.5 its close enough to melt the media
in my kalk reactor as long as its north of 11 i know it doesnt need to be refilled. 11. 7 to 12.2 is close enough.

thats the only 2 things i use ph probes for in my reef .. alk on the other hand i do care about accuracy very much .
 
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What's more important is repeatability.
+- .2 is really not usable. That is a spread of .4. I have 2 probes. If I calibrate them both to 10 and 7, and one of them reads 9 correctly. Should be a usable number and would give me a probe that is more right than the other. Big assumption that all 3 calibration fluids are correct.

while it is important to have a repeatable result. I think having a range as large as .4 accuracy is really not useful. I am also in no way convinced that the manufacturers are claiming worse than -+.1. And I will try some things to get my situation into that range.
 
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to the point that the reef keeping devices are not accurate enought , not accurate enough for what?

in my reef i use ph probe in the calcium reactor (and i dont care if its 6.2 or 6.4 or 6.5 its close enough to melt the media
in my kalk reactor as long as its north of 11 i know it doesnt need to be refilled. 11. 7 to 12.2 is close enough.

thats the only 2 things i use ph probes for in my reef .. alk on the other hand i do care about accuracy very much .
I am concerned with the ph of my reef water . Yes I guess it would be okay for calcium reactor or kalk.

I firmly believe accuracy of ph is more important than alkalinity. A ph of 8.3 easily gives twice the coral growth of 7.9 and much better overall health. Lots of studies confirm this. Brs has a good series on it. And I have recorded undeniable results as well.
Corals do okay in a very large alkalinity range. I do believe alkalinity precision and stability to be the important factor. Which is why I have a kh director testing alk 6 times a day. Less concerned if my alk is 7.5, 8.5, or 9.5 with a given reading, as long as my readings are precise. Consistency with alk, and high ph are what I have found to be very important.
 

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+- .2 is really not usable. That is a spread of .4. I have 2 probes. If I calibrate them both to 10 and 7, and one of them reads 9 correctly. Should be a usable number and would give me a probe that is more right than the other. Big assumption that all 3 calibration fluids are correct.

while it is important to have a repeatable result. I think having a range as large as .4 accuracy is really not useful. I am also in no way convinced that the manufacturers are claiming worse than -+.1. And I will try some things to get my situation into that range.

To get the most accurate measurement from your GHL probe, it needs to be freshly cleaned and freshly calibrated right before measurement. That reading may be accurate within +/- 0.1. Other probes don't claim +/- 0.1 and often don't provide an accuracy.

I assess my probe against outdoor aerated water every couple months to see real-world accuracy of the probe. If it's within +/- 0.1, I leave it be. If it's outside that range (mostly), I clean and recalibrate. If I find the readings drifting significantly outside of expected reading after calibration...time for a new probe. My last GHL probe lasted 6 months.
 
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To get the most accurate measurement from your GHL probe, it needs to be freshly cleaned and freshly calibrated right before measurement. That reading may be accurate within +/- 0.1. Other probes don't claim +/- 0.1 and often don't provide an accuracy.

I assess my probe against outdoor aerated water every couple months to see real-world accuracy of the probe. If it's within +/- 0.1, I leave it be. If it's outside that range (mostly), I clean and recalibrate. If I find the readings drifting significantly outside of expected reading after calibration...time for a new probe. My last GHL probe lasted 6 months.
Doesn’t aeration of outside air give a fairly wide acceptable range? How can you tell if it is only off by a decimal point or two?

to be clear I have never done this and am not inferring I know the answer.
 

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According to earlier posts the GHL is +\-.1. The issue here is bean animal is saying that is a rounded number because of temperature and rounding of the probe to .1 decimal points actually means it is only accurate to +-.2
Please stop repeating this. That is not what I said by any stretch of the imagination you have conflated 20 different posts and are spouting utter nonsense. It is beyond frustrating at this point.

You have dismissed, ignored, confused, conflated or distorted every fact in this thread, including that which was posted by the forum moderator and expert chemist who has intimately more knowledge about pH measurements than you or any of us.
 
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What's more important is repeatability.
I have been monitoring this thread and laughing my A** off. Finally someone gave an answer that really matters. "REPEATABILITY". I have a GHL P4 with two PH probes, two Temp probes, one Redox and one Conductivity ( which I recently broke during a calibration ) and the PH probes are normally only 0.01 difference from each other and have never exceeded 0.02.
I have more to say especially when it comes to Automatic Temp Compensation for PH but don't really want to get too involved in the thread. I will only say that I have run a test in the past and can say that the ATC calculation in the P4 is pretty darn accurate and so is the published +/-0.1 accuracy for PH from Vinny.
 
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Please stop repeating this. That is not what I said by any stretch of the imagination you have conflated 20 different posts and are spouting utter nonsense. It is beyond frustrating at this point.

You have dismissed, conflated or distorted every fact in this thread, including that which was posted by a the forum moderator and expert chemist who has intimately more knowledge about pH measurements than you or any of us.
Dude I am so freaken done with you. Go away. I just counted 6 times where I said the above about you claiming rounding and .2 and you have not once clarified until now that was not your stance. Hours of arguing over nothing because you are so high on your horse that you refuse to clarify your stance after you saw me post over and over again.

And you convolute everything I say. Just as you did again if you are referring to Randy. I agreed with everything he said and there is a post to prove it.
Go screw up somebody else’s thread you’re not welcome here.
 
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Repeatability has been mentioned several times.. Sadly, that is not his issue.
 

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Doesn’t aeration of outside air give a fairly wide acceptable range? How can you tell if it is only off by a decimal point or two?

to be clear I have never done this and am not inferring I know the answer.

There is a mathematical model for pH/Alk/CO2 in seawater. Outdoor air is ~400ppm CO2. My Alk measurement is typically 7.7 +/- 0.5 (accuracy of typical Alk measurements). So.l my Alk is somewhere between 7.2 and 8.3.

SmartSelect_20230208_191741_Pydroid 3.jpg


SmartSelect_20230208_191915_Pydroid 3.jpg


So outdoor aerated tank water should be between 8.23 and 8.28 NBS. If my pH meter is lower than 8.13 or higher than 8.38 it gets recalibrated.
 
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There is a mathematical model for pH/Alk/CO2 in seawater. Outdoor air is ~400ppm CO2. My Alk measurement is typically 7.7 +/- 0.5 (accuracy of typical Alk measurements). So.l my Alk is somewhere between 7.2 and 8.3.

SmartSelect_20230208_191741_Pydroid 3.jpg


SmartSelect_20230208_191915_Pydroid 3.jpg


So outdoor aerated tank water should be between 8.23 and 8.28 NBS. If my pH meter is lower than 8.13 or higher than 8.38 it gets recalibrated.
Okay that is helpful thanks
 
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I have been monitoring this thread and laughing my A** off. Finally someone gave an answer that really matters. "REPEATABILITY". I have a GHL P4 with two PH probes, two Temp probes, one Redox and one Conductivity ( which I recently broke during a calibration ) and the PH probes are normally only 0.01 difference from each other and have never exceeded 0.02.
I have more to say especially when it comes to Automatic Temp Compensation for PH but don't really want to get too involved in the thread. I will only say that I have run a test in the past and can say that the ATC calculation in the P4 is pretty darn accurate and so is the published +/-0.1 accuracy for PH from Vinny.
Repeatability is of course important. But repeatability of wrong numbers is not helpful.

Apparently I just had a 3 hour argument with a guy about how I thought he was wrong about these probes having a -+.2 acceptable range when that wasn’t even his opinion.

So yeah repeatability of +-.1 is important and will work just fine.
 

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I have been monitoring this thread and laughing my A** off. Finally someone gave an answer that really matters. "REPEATABILITY". I have a GHL P4 with two PH probes, two Temp probes, one Redox and one Conductivity ( which I recently broke during a calibration ) and the PH probes are normally only 0.01 difference from each other and have never exceeded 0.02.
I have more to say especially when it comes to Automatic Temp Compensation for PH but don't really want to get too involved in the thread. I will only say that I have run a test in the past and can say that the ATC calculation in the P4 is pretty darn accurate and so is the published +/-0.1 accuracy for PH from Vinny.
This has not been my luck with GHL probes...of course there could be electrical interference or something making my experience suboptimal.
 

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Dude I am so freaked done with you. Go away. I just counted 6 times where I said the above about you claiming rounding and .2 and you have not once clarified until now that was not your stance. Hours of arguing over nothing because you are so high on your horse that you refuse to clarify your stance after you saw me post over and over again.

And you convolute everything I say. Just as you did again if you are referring to Randy. I agreed with everything he said and there is a post to prove it.
Go screw up somebody else’s thread you’re not welcome here.
I have actually stated numerous times that you are misstating and/or not understanding what I (and others) are trying to explain to you.

Several people here have attempted numerous times to help you understand what +/- .1 accuracy means in context to what your instrument displays and how that reading compares to the actual pH.

Try this:

If we take TWO +/- .1 pH probes that are guaranteed to be +/- .1 ph Unit of the actual fluid.

You measure a sample with YOUR probe and it reads 8.1
the actual value could be 8.0, 8.1 or 8.2
The range from 8.0 to 8.2 is .2
You don't know what value is correct, it could be anywhere between 8.0 and 8.2

I come to your house and measure the same sample with my +/- .1 probe.
my probe reads 8.2
the actual value could be: 8.1, 8.2 or 8.3
The range from 8.1 to 8.3 is .2
I don't know what value is correct, it could be anywhere between 8.1 and 8.4

Both probes are reading within their specified accuracy.


IMPORTANT:
You can't see my probe reading and I can't see your probe reading. But both probes are accurate to +/- .1
Which reading is correct and which probe is correct? BOTH ARE!

Are you beginning to see the problem?

Bonus: We share our readings with each other. We now know that we both have ACCURATE readings within specified tolerances, our combined possible values are between 8.0 and 8.4! I am sure that value is between 8.1 and 8.3 but you are sure the value is between 8.0 and 8.2 We can use the fact that both probes are accurate and within tolerance and deduce that the the real pH is likely between 8.1 and 8.2 -- a range of .1

Great, if we already know both probes are accurate. But if we don't then we are back to where we started.

That is - if your probe, used alone IS accurate, it is telling you within .2, not .1 what the pH is.
 
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