Is it possible to determine aquarium CO2 levels ?

[Wtyson254]

Is there a way to Test aquarium CO2 levels? Or can it be calculated knowing the aquariums Alk and PH?



*** the main reason why I am asking is that I am wondering if it would be beneficial for me to start a cheato reactor on my tank as a form of CO2 uptake. I DO NOT have issues with nutrients and would have to dose Nitrate and phosphate in order to prevent low nutrient levels.

I would rather not have to do this, as my tank is relatively stable nutrient wise.
However I am constantly fighting low PH and want to see if CO2 is the culprit.

 

[Drew Halliday]

Yes adding algae would help take up co2 when the lights on it are on. You can also look into a recirculating co2 reactor. Basically you run the air to and from your skimmer through Kalkwasser to bind the CO2 and remove it from your tank. You can also try and draw air for the skimmer from outside where there is less co2.

You could calculate CO2 based on pH and alkalinity but you don’t need to. You already know there is CO2 in the water and your pH could be raised by reducing it.

 

[Wtyson254]

Based on this calculator https://www.hamzasreef.com/Contents/Calculators/CO2LevelSalt.php

My CO2 is 1.63ppm, I am
Not sure how this compares to NSW

 

[Randy Holmes-Farley Verified Community Expert]

Normal seawater aerated with normal air has less. I assume your pH is low?

The pH is controlled by the CO2 level and the alkalinity. At 7 dKH, the pH with normal air is in the 8.1-8.2 range. A drop of 0.3 pH units is about a doubling of the CO2.

 

[Wtyson254]

So with alkalinity at 8 dKH ans pH of 7.85, would you imagine that the air CO2 is significantly higher than the 350-450pmm in outdoor air?

Also, would co2s effect on PH be of lesser or greater magnitude with a higher dKH

 

[Randy Holmes-Farley Verified Community Expert]

So with alkalinity at 8 dKH ans pH of 7.85, would you imagine that the air CO2 is significantly higher than the 350-450pmm in outdoor air?

If the tank is in equilibrium with that air, yes. Maybe twice as high.

So with alkalinity at 8 dKH ans pH of 7.85, would you imagine that the air CO2 is significantly higher than the 350-450pmm in outdoor air?

The "magnitude of the pH effect is the same, but the baseline rises as the alk rises. Double the alk (say, 7 to 14 dKH) and that offsets almost exactly a doubling in CO2 while staying at the same pH. Said differently, doubling the alk from 7 to 14 dKH causes about a 0.3 pH unit rise in pH, if the CO2 level stays the same.

 

[Drew Halliday]

Have you tried testing the pH with two independent measuring means? You may have error in the testing.

 

[BullyBee]

Drop checker is what I use but I’m not sure it would work in salt

 

[Randy Holmes-Farley Verified Community Expert]

Have you tried testing the pH with two independent measuring means? You may have error in the testing.

His pH is very commonly observed by reefers, so while it may be inaccurate, it is not unusual.

 

[Wtyson254]

I have checked it with the Apex probe (freshly calibrated), a Hannah PH drop checker, Freshly calibrated, and an Elos PH test kit. I have bulk PH calibration solution on hand And
Verify accuracy often

.

If the tank is in equilibrium with that air, yes. Maybe twice as high.



The "magnitude of the pH effect is the same, but the baseline rises as the alk rises. Double the alk (say, 7 to 14 dKH) and that offsets almost exactly a doubling in CO2 while staying at the same pH. Said differently, doubling the alk from 7 to 14 dKH causes about a 0.3 pH unit rise in pH, if the CO2 level stays the same.

Have you tried testing the pH with two independent measuring means? You may have error in the testing.

His pH is very commonly observed by reefers, so while it may be inaccurate, it is not unusual.

So I think I am starting to understand what Has happened. I have historically kept my Alk around 11-12 dKH but about 6 weeks ago i decided to bring it down closer to NSW (8 dKH). I imagine my indoor CO2 levels have not drastically changed.

 

[Wtyson254]

The CO2 concentration in my apartment is 1200ppm, @Randy Holmes-Farley is there anything I can do to try and decrease its effect on my reef ?

 

[Randy Holmes-Farley Verified Community Expert]

The CO2 concentration in my apartment is 1200ppm, @Randy Holmes-Farley is there anything I can do to try and decrease its effect on my reef ?

Open windows, use a CO2 scrubber or outside air on a skimmer inlet, use high pH additives for alkalinity, grow macroalgae or other photosynthesizers.

 

[GoVols]

The CO2 concentration in my apartment is 1200ppm, @Randy Holmes-Farley is there anything I can do to try and decrease its effect on my reef ?

If you know what your doing, with the proper (gear) ph probe and turn off switches.

Kalk can dose calcium, alk and it consumes Co2.