pH from Skimmer - Outside Air or CO2 Scrubber

[ca1ore]

For example, opening the windows to the house makes my ph jump to 8.3, but drawing fresh air through my skimmer has minimal impact. It’s interesting to think about though.

I noted earlier in this thread, and elsewhere previously, that running a fresh air line has historically made no difference to the PH in my tank. I do run a fresh air line, though mainly to muffle the sound of the dual mazzei venturi. It makes intuitive sense to me that in my system, at least, fresh air to the skimmer would make no difference. It simply not enough to offset all the open top bodies of water in my system that are absorbing CO2 from inside my house. Now, if I run a blower to exchange the room air that does make a difference. But that is only practical during the temperate months of the year. Otherwise I just don't OCD over it.

 

[markstubb]

That is correct. O2 has no effect on pH.

If you know the carbon dioxide level and the carbonate alkalinity, you can directly calculate the pH.

This has more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

and for the math part:

Chemistry And The Aquarium: The Relationship Between Alkalinity And pH ? Advanced Aquarist | Aquarist Magazine and Blog
https://www.advancedaquarist.com/2002/5/chemistry

Thanks Randy. I've read through quite a bit of your articles related to pH and its relation to Alk, and find it very fascinating. Helped me understand why some things were measuring the way they were in my tank when I expected a different result, or was formulating a plan of attack to solve a problem. That being said, can you help me understand the science behind what's happening when one uses a CO2 scrubber to feed a skimmer opposed to if I just injected 100% O2 into the skimmer, which is entirely void of CO2?

I keep my Alk around 9.5 but pH swings from 7.7 to 8.

 

[Reef Dude]

I noted earlier in this thread, and elsewhere previously, that running a fresh air line has historically made no difference to the PH in my tank. I do run a fresh air line, though mainly to muffle the sound of the dual mazzei venturi. It makes intuitive sense to me that in my system, at least, fresh air to the skimmer would make no difference. It simply not enough to offset all the open top bodies of water in my system that are absorbing CO2 from inside my house. Now, if I run a blower to exchange the room air that does make a difference. But that is only practical during the temperate months of the year. Otherwise I just don't OCD over it.

So you’re skimmer pulls enough air to make a difference when hooked up to the scrubber, it when it pulling the same air volume of fresh air, it doesn’t make a difference. Me too. That’s what I think it is interesting. You’d think if fresh air into skimmer doesn’t make a difference, then a co2 scrubber wouldn’t make a difference either

 

[ca1ore]

I would imagine the point is that o2 has no inherent affect on PH; though running pure o2 would of course avoid any incidental co2 that's in the fresh air. The whole blowing yourself to bits seems like a reason not todo it

 

[markstubb]

I would imagine the point is that o2 has no inherent affect on PH; though running pure o2 would of course avoid any incidental co2 that's in the fresh air. The whole blowing yourself to bits seems like a reason not todo it

Of course it's a bad idea - I'm just still confused as to why a scrubber would be more effective than pure O2. Hell, Argon, anything that doesn't have CO2 should work I suppose.

I now understand that outside air has less CO2 than inside air, but the volume of air exchange happening at the top of tank and sump, or any exposed water surface, is really the issue. It seems that removing ALL CO2 is what makes the skimmer more effective than just "less" CO2 from outside air.

 

[ca1ore]

It seems that removing ALL CO2 is what makes the skimmer more effective than just "less" CO2 from outside air.

I think that's right.

 

[ca1ore]

So you’re skimmer pulls enough air to make a difference when hooked up to the scrubber, it when it pulling the same air volume of fresh air, it doesn’t make a difference. Me too. That’s what I think it is interesting. You’d think if fresh air into skimmer doesn’t make a difference, then a co2 scrubber wouldn’t make a difference either

Yes, though I gave up on the scrubber years ago. Just too much of a pain constantly replacing the depleted media. One way to help boost pH is to use Kalk.

 

[Randy Holmes-Farley]

But to your initial point, I don’t understand why the outside air line alone doesn’t solve ph problems (or perceived problems). For example, opening the windows to the house makes my ph jump to 8.3, but drawing fresh air through my skimmer has minimal impact. It’s interesting to think about though.

The tank top is aerated with bad air against the skimmer using good air. It's never obvious, in advance, which wins, but if you drive CO2 even lower in the skimmer air, that helps it win.

 

[jrlafrance]

This maybe a dumb question, but if opening your windows helps with the pH swing, wouldn't putting a fan in the sump area to help bring in "fresher" air help too? At least a little bit, right?

 

[jrlafrance]

Sorry, double post.

 

[Randy Holmes-Farley]

This maybe a dumb question, but if opening your windows helps with the pH swing, wouldn't putting a fan in the sump area to help bring in "fresher" air help too? At least a little bit, right?

Maybe, if the sump air has more CO2 than the room air.

 

[chema]

I can verify the observations previously stated in this thread. My tank has always suffered of low pH, typically between 7,7 (night) and 8 (day). And I could get that by using a generous amount of kalkwasser. I built a CO2 scrubber using an old Two Little Fishes reactor filled with soda lime (around 600 ml). The impact on pH was like magic, around o,2 more, both in the lower and higher limits, but at the cost of having to replace the soda lime each 4 days. A lot of effort and a high cost.

Afterwards I decided to run an outside line to the skimmer silencer, thanks to an opening in the wall next to my tank. My hope was to get the same result than that achieved by means of the CO2 scrubber, but that was not true. I could hardly see any pH increase from the initial situation without the scrubber.

A couple of months ago my kalkwasser reactor broke down and the pH problem got even worse. Instead of replacing the reactor I gave a try to the new Randy's two-part recipe and that has worked great (thanks Randy!). I got a pH range better than with kalkwasser. Finally I decided to also try the CO2 scrubber again in between the skimmer silencer and the outside air line. The result has been impressive. Now my ph goes from 7,95-8,0 at night and 8,25 at day. Next challenge is to check how long the soda lime lasts. My expectation is that longer than in my first experiment, as the outside air should contain much less CO2 than the inside air, but who knows. If the 600 ml of the Two Little Fishes reactor last for a week or so I may consider buying a comercial CO2 scrubber like the 3 l one sold by Pacific Sun. That should last for more than a month, making it much more convenient from the economics and labour point of view.

 

[JDowns]

A properly implemented scrubber with humidity can reduce the CO2 to nearly half that of nominal outside CO2 levels.

 

[chema]

A properly implemented scrubber with humidity can reduce the CO2 to nearly half that of nominal outside CO2 levels.

I would like to be able to measure the CO2 content of outside air and the CO2 content of the air entering the skimmer after exiting the scrubber, but, qualitatively, my result confirms your statement. However I have not tried the humidity trick yet.

Would a little water at the bottom of the reactor be enough or would it be better to use an additional reactor filled with water?

 

[Chad3407]

I found pulling air from the skimmer cup to the scrubber to be the best for me. I tripled the scrubber media life and pH stays between 8.0 and 8.15. with out a scrubber my tank would drop down to 7.7 at night.

 

[JDowns]

I would like to be able to measure the CO2 content of outside air and the CO2 content of the air entering the skimmer after exiting the scrubber, but, qualitatively, my result confirms your statement. However I have not tried the humidity trick yet.

Would a little water at the bottom of the reactor be enough or would it be better to use an additional reactor filled with water?

A little bit of water in the bottom certainly helps and it prolongs the life of the media. I've completed two tests one with dry air and one with humid air. Currently running a test with air recirculated from the skimmer. You can see results here.

https://www.reef2reef.com/threads/co2-scrubber-testing.482361/page-3

 

[chema]

A little bit of water in the bottom certainly helps and it prolongs the life of the media. I've completed two tests one with dry air and one with humid air. Currently running a test with air recirculated from the skimmer. You can see results here.

https://www.reef2reef.com/threads/co2-scrubber-testing.482361/page-3

Thanks a lot JDowns. Great thread and great reading. If I got it right you doubled the lifetime of the media when adding water to the bottom of the reactor. I'll try that first before drilling the cup of the Bubble King and do the skimmer recirculation trick

 

[JDowns]

Thanks a lot JDowns. Great thread and great reading. If I got it right you doubled the lifetime of the media when adding water to the bottom of the reactor. I'll try that first before drilling the cup of the Bubble King and do the skimmer recirculation trick

Sounds like a solid plan. The skimmer test should be complete in about two weeks.

Yes there was a doubling of media life and an increase in production.

 

[chema]

Sounds like a solid plan. The skimmer test should be complete in about two weeks.

Yes there was a doubling of media life and an increase in production.

I'll be waiting for the results of the skimmer test. In the meantime I'll see whether I can reproduce your former results. Just doubling the lifetime of the media would be terrific.

Thanks a lot!