CO2 in house is driving tank pH down

[zear0]

Hey All,

I've noticed my pH trending down since the cold weather started. I did the air stone in a cup of tank water test a few weeks ago and found that the pH drop is due to CO2. I opened the windows in my house on a warm day and the pH in the tank came back up after several hours.

I'm wondering if anyone else has this problem and has a solution for it besides opening the windows periodically during the winter.

One recommendation I've gotten so far is to pull the air for the protein skimmer from outside. I might be able to swing this setup, but am wondering if there might be something easier/nicer looking than running an airline from the tank to outside.

 

[NateHanson]

What's the "airstone in a cup of tank water test", and how does it implicate CO2?

What was your pH a few months ago, and what is it now? And have you recalibrated your meter or checked with another meter?

 

[zear0]

The air-stone test was recommended on several threads I've read about low pH. Basically, you take a cup of tank water , set it outside with an airstone in it and aerate it for several hours. Afterwards, you check the pH. If it goes up, that indicates an aeration problem.

Two weeks ago, when my pH was low the first time, I did some research and found some comments about homes with tight seals on the windows having a higher CO2 concentration in them. This higher CO2 concentration increases the CO2 in the tank water and affects the pH negatively. So, I tried opening the windows in my house for a day and joila, the pH was back to where it was during the summer.

I've recalibrated my pH monitor (its 10 weeks old) monthly since I received it. I also spot check it with a chemical pH test kit once a week. It's always been spot on.

My pH during the summer was 8.2 daytime down to 8.0 nightime. Now it is 8.0 daytime down to 7.8 nighttime. Opening the windows fixed it last time, but with winter approaching, this won't be a practical option.

Am I barking up the wrong tree with the aeration here?

 

[NateHanson]

Do you use Kalkwasser for topoff? That would get your pH a bit higher, and may be a lot easier than breathing less.

 

[Armando]

You can also put lots of plants in the house

 

[zear0]

I'm not topping off with kalk, but I can look into that. This may likely fixthe pH, but not the high CO2 to O2 ratio in the tank.

 

[NateHanson]

I'm not sure I see any evidence that you have a high CO2 to 02 ratio in the tank? Are you basing that on the 0.2 pH difference compared to summer?

If you have a skimmer and a sump, I'm sure your water has no problem with gas exchange. All that bubbling and tumbling ensures thorough exchange of gases to equilibrium with the ambient air. I'd just bump your pH up a bit with Kalk, or with a reef buffer.

What's your alk by the way?

 

[starrfish]

The "test" is Randy's and is documented in this article:

http://www.reefkeeping.com/issues/2004-09/rhf/index.php

I have an airline running from my skimmer to the outside and it does help to keep the ph up.

 

[zear0]

The problem is the air in the house is higher in CO2 than outside air. So, no matter how much of the house air I push into the tank, it will not change the CO2 to O2 ratio of the tank.

I am concerned about the .2 drop because it is a trend... I am not sure how low it will go, but I need a permanent solution for the winter when leaving windows in the house open isn't an option.

I am looking for methods people have used to either get air from outside directly into their tanks or a means for ventilating the CO2 out of the house and bringing O2 back up.

Starrfish, is your skimmer fed air by a venturi? Does the length of the airline affect the venturi's ability to draw air in? The closest window to my tank is ~6 feet away.

 

[NateHanson]

The problem is the air in the house is higher in CO2 than outside air.
I am looking for methods people have used to either get air from outside directly into their tanks or a means for ventilating the CO2 out of the house and bringing O2 back up.

I don't mean to question the reasoning of others on various bulletin boards, but this all seems awfully speculative. You aren't measuring O2 or CO2 in your tank or in your house, and you don't even know if small differences in the relative ratio of those gases is important to your tank, yet you're concluding that there's an imbalance in the ratio of those. I would simply work to fix the problem that you've measured - low pH. Otherwise you're throwing solutions at problems that aren't really there, and that can just make things worse. Stick with what you know, and can measure.

Just my 2 cents, and what's more, they're free!

 

[zear0]

I hear ya Nate. Your advice is sound and respected... I do plan to start dosing Limewater, per your advice, to help stabilize my pH and bring my alkalinity up.

On the other boards, (reefs.org and wetwebmedia) people are very quick to raise the CO2 O2 issue whenever someone posts about low pH problems. I've done several "experiments" with aerating my tank water with outdoor air and seen the pH rise every time. This is why I am so adamant about following through with the "fresh air" approach.

If I aerate my tank with outdoor air through the winter, there will be less of a pH swing when summer roles around and I start opening the windows again. I hope this translates to less tweaking of the kalk dosing due to the changing CO2 concentrations in my house. I think this is a reasonable, two pronged approach.

Good Discussion... Thanks for the help all