Organic Carbon Dosing and CO2 Production

[Brandon McHenry]

Hi all! I know that dosing organic carbon has a negative impact on pH, either by an immediate decrease (like adding vinegar) or eventual when it’s metabolized and CO2 is produced. My question is how much of an impact does organic carbon dosing have on pH through the production of CO2 only (I’m not using vinegar so there is no immediate reduction)? How long before the impact is seen? Can it be mitigated? Thanks in advance!

 

[Randy Holmes-Farley Verified Community Expert]

It's complicated.

The overall effect is the same for vinegar and vodka for the same number of molecules metabolized (and is larger than the vinegar sudden drop when first added). But the sudden drop from vinegar is easy to see. The drop from slower metabolism is very hard too see accurately because the tank is constantly changing in CO2 levels for other reasons (photosynthesis, other respiration, etc.).

Mostly because organic metabolism consumes O2, and partly because it lowers pH, I advise dosing during the daytime in a reef tank.

 

[Brandon McHenry]

It's complicated.

The overall effect is the same for vinegar and vodka for the same number of molecules metabolized (and is larger than the vinegar sudden drop when first added). But the sudden drop from vinegar is easy to see. The drop from slower metabolism is very hard too see accurately because the tank is constantly changing in CO2 levels for other reasons (photosynthesis, other respiration, etc.).

Mostly because organic metabolism consumes O2, and partly because it lowers pH, I advise dosing during the daytime in a reef tank.

I assumed it was complicated, thank you for clarifying! So it’s probably advisable to dose when the lights are just coming on as opposed to in the evening with feeding? I ask because while I may get my pH up to 8.1-8.2 at night (with ESV b-ionic, kalkwasser and a CO2 scrubber) the pH drops to 7.7-7.8 in the morning. Just wondering if the organic carbon is hurting my efforts or if it might just be the time I’m dosing.

 

[Dan_P]

Hi all! I know that dosing organic carbon has a negative impact on pH, either by an immediate decrease (like adding vinegar) or eventual when it’s metabolized and CO2 is produced. My question is how much of an impact does organic carbon dosing have on pH through the production of CO2 only (I’m not using vinegar so there is no immediate reduction)? How long before the impact is seen? Can it be mitigated? Thanks in advance!

If you have a doser, add the daily dose over the entire day. This will minimize the chance of any surge in oxygen consumption and CO2 production.

 

[Pistondog]

I didn't see the co2 induced ph drop from carbon dosing as a huge/noticable effect. Mitigate with good air exchange, skimmer.

Dosed several times/day

 

[Brandon McHenry]

If you have a doser, add the daily dose over the entire day. This will minimize the chance of any surge in oxygen consumption and CO2 production.

I didn't see the co2 induced ph drop from carbon dosing as a huge/noticable effect. Mitigate with good air exchange, skimmer.

Dosed several times/day

Maybe my issue is not spreading out the dose. Maybe doing it all at once towards the end of the day is part of the problem. I know I do struggle with depressed pH due to CO2 in a tightly sealed home so this may be compounding my problem.