High CO2 in Ambient Air

[marsh]

Not that I have this problem, but I thought of a potential solution for those that do. High indoor CO2 may lead to abnormally low PH in conjunction with adequate alkalinity.

Solutions involve opening a window, venting outside air to a skimmer, and limewater. http://www.reefkeeping.com/issues/2004-09/rhf/index.php

Along the lines of venting to a skimmer I thought perhaps using a CO2 filter, sodasorb (soda lime....Sodium Hydroxide) like what is used on anesthesia machines, for the airtake of a skimmer. I believe this was also used on Apollo 13 to lower toxic levels of CO2.

Anyway, to those that know...would this work?

 

[Randy Holmes-Farley]

Yes, that can work, but you need one with a pretty large air flow and may be technically challenging. I've suggested it to some folks, but I do not know of anyone who did it and posted back any results. I'd probably dissolve the sodium hydroxide in fresh water to make it react faster with air bubbled through it.

 

[marsh]

I have gerry-rigged a sodasorb filter attached to my skimmer...we'll see if it raises my PH from 8.1. The skimmer is bubblin well so the air flow must be OK.

If I were to see a result how long would I need to run it?

 

[reefkeeper2]

How did you do it? Can you post a pic?

 

[marsh]

Below is my C02 scrubber. It consists of a GE Medisorb anesthesia cartridge jammed inside a suction bucket. You can see the tubing coming out of the red top bucket leading to the skimmer air inlet. I cut a hole in the bottom of the suction bucket. A Milwaukee PH probe is in the other end of the sump/rugium (? accurate to 0.1 PH changes)

I have got a hunch that this will not do it in a large system. Mine is a 240 G (96x24x24) plus 75 G sump/refugium...total water volume ~250 G after you take into account sand, rock, etc. Anyway, I thought I read something by Eric Borneman recently on experimentation with different sized systems and O2 levels...skimmer didn't seem to help O2...maybe this is also the case with CO2. The idea with the CO2 scrubber attached to the skimmer would be that the majority of CO2 exchange would go on in the skimmer rather than other gas/liquid interfaces. However, people using CA++ reactors sometimes empty the effluent into a skimmer to evacuate excess CO2 and minimize PH drop....so maybe this idea isn't so screwy.

 

[Randy Holmes-Farley]

A day is plenty to see an effect.

Here are some older threads on CO2 scrubbers:

http://reefcentral.com/forums/showthread.php?s=&threadid=116479

http://www.reefcentral.com/forums/showthread.php?threadid=532444

http://www.reefcentral.com/forums/showthread.php?threadid=99629

 

[reefkeeper2]

Good thread. What I would like to do is prevent the CO2 from getting into the tank water in the first place. Hard to do if you have a reactor. I have a suspicion that elevated CO2 levels in the tank water help drive unwanted algal and cyano growth. My pH runs 8.0-8.2. I vent the skimmer with outside air. I did an experiment with an venturi to see if more aeration (in the sump) with outside air would raise the pH further. It didn't.
If the CO2 in the room is still high, the tank is going to try and equilibrate with the air around it in the room. I think that venting the skimmer helps, but not much. Even if the room CO2 levels were the same as that outdoors, there would still be higher levels in your tank because of the reactor. So the question is, how do you get some of the CO2 out of the effluent of your reactor before it goes into your tank? Sending it throught he skimmer doesn't seem to help much.

 

[marsh]

I have no idea if the scrubber actually worked but the PH changed over the past ~24 hrs from 8.1 to 8.2. Might be useful to follow up with strict controls....

The tank is relatively young..does not have a calcium reactor installed yet...but it will soon. Does have a reverse lighting refugium with macro algae. Nothing was added other than fish food in the last 24 hours. I do have 8 relatively large SPS corals in the tank...

 

[Randy Holmes-Farley]

Sounds good. Keep us updated.
So the question is, how do you get some of the CO2 out of the effluent of your reactor before it goes into your tank? Sending it throught he skimmer doesn't seem to help much.

Some people aerate the effluent, but that requires some engineering, and is the home has excess CO2, may not help much.