Fresh Air and pH

[morpheas]

It has been stressed time and time again the importance of refreshing the house air with outside air to help raise a tank's pH, especially for tanks which are struggling with low pH. A lot of people also run airlines from their skimmers to the outside just to reap the benefit. More on the science behind the effect here.

The reason for this thread is more of a visual aid to the aforementioned relationship. Below, you will see a picture of my Apex monitoring. The left circle indicates a "regular" pH rise from the time the lights come on (the spike right after the turnaround is the dosing of my alkalinity buffer). The second circle shows a day where the door to the back yard was opened for 30 minutes. Note that the lights are not on during that period! The pH kept on going up even after the door was closed. The air in the house had been refreshed and that's what mattered. You will be see clearly the effect of fresh air in the house from a pH standpoint (oxygenation, CO2 removal etc).

Like I said, I'm sure it has been hammered in to many reefers' minds by now but seeing it like this might make a lot of people double check if they need to really do anything drastic - and probably unnecessary or harmful - for their pH (dosing, buffers etc).

 

[ScoobyFish]

Does the tank stabilize to its own neutral ph if it Indeed went down from lack of oxygen, or will the ph keep rising if I were to run air line to skimmer?

 

[morpheas]

The swing in pH is a natural phenomenon related mainly with the photo period. When lights are on the zooxanthellae photosynthesize reducing the CO2 in the water, naturally increasing the pH. When the lights are out, the opposite happens. That is the main driving force that a lot of people choose to run their refugium lights on opposite times of the display.

Gas exchange with the room removes the excess CO2 from the water and replenishes with fresh air. The content of the fresh air in CO2 will determine how much of the "acidic" CO2 is removed from the water column and what will the equilibrium between the two will be. The "fresher" the air the less will stay behind, the higher the pH will be. Of course, under normal circumstances, there is a limit to the shift in the value. When I don't open my door, the room becomes more saturated with CO2 (within normal levels because I can breathe!) thus the absolute value drops. When I open a window/door or run an air line outside from my skimmer I am introducing "fresher" air (again within normal limits, the fresh air is not entirely without acidic compounds, for instance CO2) I increase the absolute value of the pH because the equilibrium content of CO2 now in the water is less.

Of course, you can push this phenomenon further out of "normal" and we definitely do that in the hobby, the biggest example being calcium reactors. There CO2 is used to titrate the water that goes into the reactor dropping it's pH down to an acidic level where calcium carbonate dissolves (in the 6 neighborhood).

So, the answer to the question I guess is that by running the line, you will move that average of the swing higher from what it would be.

I hope I made a little sense

 

[ScoobyFish]

makes alot of sense, i kinda already suspected this, but you put it more clearly. its what made me wonder how outside air affects my tank, since i live in major city and not only that but there is a very busy expressway just a block away, nearly all day its car pollution, but i guess the air inside is more polluted, i dont know ima hafta find a way around this i guess.

 

[beaslbob]

IMHO the best thing is to balance out and stabilize the system with algae be it macros, corraline, or an algae turf scrubber.

In that way the tank becomes a net consumer of co2 and supplier of oxygen to the surrounding air.

depending on alk sure pH can rise and fall each day.

But I'm not aware of any fish and corals that don't thrive in a low co2 high oxygen environment.

BTW IME my lowest pH with macros was still much higher (8.0 api high range kit) then my highest ph before adding macro algaes (7.7 or so). Even with a nightly ph drop before I raised alk with baking soda. after increasing alk I tested 8.4-8.8 (api high range kit) day and night.

 

[morpheas]

makes alot of sense, i kinda already suspected this, but you put it more clearly. its what made me wonder how outside air affects my tank, since i live in major city and not only that but there is a very busy expressway just a block away, nearly all day its car pollution, but i guess the air inside is more polluted, i dont know ima hafta find a way around this i guess.

The air in the room is more saturated with CO2 because it's a closed system (the better insulation your house has the less the gas exchange with the outside). Unless you live in Beijing you'll probably have better air outside than inside. What @beaslbob says though about the refugium is probably a better way to combat it.

IMHO the best thing is to balance out and stabilize the system with algae be it macros, corraline, or an algae turf scrubber.

In that way the tank becomes a net consumer of co2 and supplier of oxygen to the surrounding air.

depending on alk sure pH can rise and fall each day.

But I'm not aware of any fish and corals that don't thrive in a low co2 high oxygen environment.

BTW IME my lowest pH with macros was still much higher (8.0 api high range kit) then my highest ph before adding macro algaes (7.7 or so). Even with a nightly ph drop before I raised alk with baking soda. after increasing alk I tested 8.4-8.8 (api high range kit) day and night.

Agreed. I don't have a refugium setup for other reasons but buffering pH would be a good motivation. It would make the tank self sufficient in that way and much more stable.

 

[beaslbob]

...



Agreed. I don't have a refugium setup for other reasons but buffering pH would be a good motivation. It would make the tank self sufficient in that way and much more stable.

Actually, just to be clear incase someone read this 5 years from now, my pH (before the alk increase) actually had a much larger ph nightly drop. I went from 8.4-8.8 to 7.9 (api high rang test kit). After boosting the alk for nightly ph drop was mush less and almost entirely eliminated.

My little pet peeve is that constant and stable are actually two different things. Before boosting the alk, the nightly pH drop was hardly constant but more stable because should it drop more in a given night the tank would react to restore the original ph drop.

By contrast I had a much more constant pH of 7.7-7.5 before the macro algaes. So much more constant but IMHO much less stable. So should something go bump in the night, the pH would tend to drop even further.

Just an old geeky engineer's observation.

 

[Randy Holmes-Farley Verified Community Expert]

Actually, just to be clear incase someone read this 5 years from now, my pH (before the alk increase) actually had a much larger ph nightly drop. I went from 8.4-8.8 to 7.9 (api high rang test kit). After boosting the alk for nightly ph drop was mush less and almost entirely eliminated.

My little pet peeve is that constant and stable are actually two different things. Before boosting the alk, the nightly pH drop was hardly constant but more stable because should it drop more in a given night the tank would react to restore the original ph drop.

By contrast I had a much more constant pH of 7.7-7.5 before the macro algaes. So much more constant but IMHO much less stable. So should something go bump in the night, the pH would tend to drop even further.

Just an old geeky engineer's observation.

The size of the daily swing is close to linearly related to the alkalinity: higher alk means more pH buffering and a smaller pH swing.

Lower average pH also means a greater swing since seawater is best buffered at higher pH.

 

[Randy Holmes-Farley Verified Community Expert]

It has been stressed time and time again the importance of refreshing the house air with outside air to help raise a tank's pH, especially for tanks which are struggling with low pH. A lot of people also run airlines from their skimmers to the outside just to reap the benefit. More on the science behind the effect here.

The reason for this thread is more of a visual aid to the aforementioned relationship. Below, you will see a picture of my Apex monitoring. The left circle indicates a "regular" pH rise from the time the lights come on (the spike right after the turnaround is the dosing of my alkalinity buffer). The second circle shows a day where the door to the back yard was opened for 30 minutes. Note that the lights are not on during that period! The pH kept on going up even after the door was closed. The air in the house had been refreshed and that's what mattered. You will be see clearly the effect of fresh air in the house from a pH standpoint (oxygenation, CO2 removal etc).

Like I said, I'm sure it has been hammered in to many reefers' minds by now but seeing it like this might make a lot of people double check if they need to really do anything drastic - and probably unnecessary or harmful - for their pH (dosing, buffers etc).

Nice graph.

 

[beaslbob]

The size of the daily swing is close to linearly related to the alkalinity: higher alk means more pH buffering and a smaller pH swing.

Lower average pH also means a greater swing since seawater is best buffered at higher pH.

Thanks

Still just my observation.

I had much less pH swing before I added the macro algae. and much higher pH after adding the macro algae. Then the alk dropped over time and I noticed the swing increased. After dosing baking soda the swing lessoned.

Could also be dependant on the api test kits also especially the pH kit.

I suspect co2 levels was an overriding factor.

but that's just me and my .02

 

[Randy Holmes-Farley Verified Community Expert]

Thanks

Still just my observation.

I had much less pH swing before I added the macro algae. and much higher pH after adding the macro algae. Then the alk dropped over time and I noticed the swing increased. After dosing baking soda the swing lessoned.

Could also be dependant on the api test kits also especially the pH kit.

I suspect co2 levels was an overriding factor.

but that's just me and my .02

Yes, those are the expected results from macroalgae using CO2.

 

[morpheas]

For the sake of completeness here is the full day cycle for two consecutive days. The pH low is similar (7.95 vs. 8) but the apex is quite some distance 8.09 vs. 8.2

 

[CoralNerd]

I open my house up basically 365 days a year as I live in a mild climate. I installed a whole house fan and when I open the windows the fresh air gets drawn in then kicked out through a vent in the hall and out of the attic. My ph for sure benefits by this.

I know a lot of talk in the forums has gone on about micro bubbling, and I tell you my ph has never been more stable since I started bubbling. Coral growth greatly improved also.

That airline to protein skimmer sounds sweet but I'm not sure how I would do that in my house.