PH confusion

Panicked Reefer

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I have been using a red sea PH test for over a year. It read 8.2 24/7. I have been suspect of this but the tank has not shown any ph related issues that I am aware of and figured the test was not sensitive enough to show the fluctuations so I was not all that concerned. I have had plenty of issues but none that I know are tied to low PH. I am planning to try kalkwasser so I decided to get another test to feel more confident in my PH level. I landed on the Hannah PH checker. This is reading 7.6. Ran the RS test simultaneously and it showed 8.2. I did this 3x with the same results. Am I to assume my tank has been running at 7.6? I may not be aware of some of the side effects of low PH, what should I be watching out for?
 
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mdb_talon

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It is extremely unusual for a tank to stay at the same ph 24/7 so for that reason alone i would be suspicious of that 8.2 reading you had been getting. Of course that dont make your 7.6 number right necessarily....they could both be wrong.
 

blaxsun

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It is extremely unusual for a tank to stay at the same ph 24/7 so for that reason alone i would be suspicious of that 8.2 reading you had been getting. Of course that dont make your 7.6 number right necessarily....they could both be wrong.
Agreed. I have the Red Sea pH test kit so I'm somewhat familiar with it. Your pH will typically drop at night, so a range of 7.9-8.2 is fairly normal (what my tank averages).
 
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Panicked Reefer

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Did you calibrate the Hannah with calibration solution? For confirmation, you could take a sample to your LFS and see what they come up with for pH.
I do not have the calibration solution. It is one of those egg checkers so I don't believe I can adjust it therefore I did not purchase it. In retrospect that would be good to validate it at least.
 
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Panicked Reefer

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It is extremely unusual for a tank to stay at the same ph 24/7 so for that reason alone i would be suspicious of that 8.2 reading you had been getting. Of course that dont make your 7.6 number right necessarily....they could both be wrong.
I agree. I suspected the red sea was somewhat erroneous. In the absence of seeing issues I could correlate with low ph I assumed it was fine whatever the number was.
 
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Panicked Reefer

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Agreed. I have the Red Sea pH test kit so I'm somewhat familiar with it. Your pH will typically drop at night, so a range of 7.9-8.2 is fairly normal (what my tank averages).
My concern with all of this is that when I took the reading where I got the 7.6 outcome on the Hannah Was approximately 2/3 of the way through my daylight schedule. This has me worried as it would dip super low when the lights are off.
 

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My concern with all of this is that when I took the reading where I got the 7.6 outcome on the Hannah Was approximately 2/3 of the way through my daylight schedule. This has me worried as it would dip super low when the lights are off.
I suspect the Hanna hasn't been calibrated properly. The Red Sea pH test is a color chart, so there's a fair amount of variation and interpretation with results.

Chances are the Hanna is reading too low and the Red Sea is off by probably 0.1. When I used my Red Sea the pH always came in at the same (8.0), but since switching to an Apex it ranged from 7.9-8.1 (it's now 7.9-8.2).
 

Erin1971Texas

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In the absence of seeing issues I could correlate with low ph...
Don't chase numbers! You definitely need to find a reliable test for pH, but if the tank looks good, I wouldn't rush to change it.
 
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mdb_talon

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My concern with all of this is that when I took the reading where I got the 7.6 outcome on the Hannah Was approximately 2/3 of the way through my daylight schedule. This has me worried as it would dip super low when the lights are off.

Ya u van definetely see the concern. I wouldnt panic though as the chances of 7.6 being correct near your high point are extremely small. If alkalinity is in range and your gas exchange is anywhere near reasonable around 7.6 would be your low. I could see wanting to improve that i just saying dont put too much faith in the number you are seeing now.
 

HawkeyeDJ

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The problem with Hanna is possibly calibration. The problem with RS is possibly color interpretation by the operator. Men are particularly subject to color blind issues.

I have app on my phone call "Aquarium Note." There is a tool for interpreting color on charts. You snap a pic of the sample color (A), then snap a pic of the chart lower than the sample (B), then snap a pic of the chart higher than the sample (C). The app will then tell you which chart color is closer to your sample color and by how much. It seems very consistent to me.
 
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Panicked Reefer

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I strongly doubt it's a gas exchange issue. I have a sump, skimmer, and fuge. My fuge light is run opposite to my dt lights. I have recently started to carbon dose. I dose 1ml of vinegar. The RS test has not registered a change before and after carbon dosing. I have read that people have complained the egg has given +.5 readings. Maybe I'm just that guy and got the one that reads -.5?
 

arking_mark

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It appears the hanna may be correct. Found an API test I had and used all 3. API-7.8; Hanna-7.8, RS-8.2

None of these test are accurate.

Do an outdoor cup aeration test...and you can calculate the pH based on 400 CO2 and you tank Alk.

It's how I assess my probes to see how off they are.
 
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I chased PH for years and regret every second (and dollar) now. I only care about PH now as a method to determine there is something out of the norm occurring. For instance, my ATO container went dry one night, so I filled the ATO container when I woke up, reset the Apex trigger, and then proceeded to push 3 gallons of topoff water through my kalk reactor raising the PH to 10. Water change !!!!
 

arking_mark

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Can you explain how to do this please?

There is a mathematical model for the CO2 ocean systems.

Basically, given any two of pH, CO2, or Alk, you can calculate the third.

Outdoor CO2 is roughly 400ppm, my tank Alk is 7.7ish...

So if I aerate a cup of my tank water outside for an hour with an airstone and trust my Alk measurement...then I should measure a pH of 8.25ish

SmartSelect_20220721-195649_Pydroid 3.jpg


For most tanks in the normal range of Alk, you should expect a reading of 8.2 to 8.3.

As most tests are pretty poor, (including my GHL pH probes), I just assess the reading. If it's lower than expected my probe is underestimating...if it's reading high it's over estimating.

That's pretty much good enough for me to regulate the tank.
 
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Randy Holmes-Farley

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this is the aeration test:


The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.
 

Randy Holmes-Farley

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I chased PH for years and regret every second (and dollar) now. I only care about PH now as a method to determine there is something out of the norm occurring. For instance, my ATO container went dry one night, so I filled the ATO container when I woke up, reset the Apex trigger, and then proceeded to push 3 gallons of topoff water through my kalk reactor raising the PH to 10. Water change !!!!

Deciding how to pursue pH changes is at least as important as deciding to do it. :)
 

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