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FAQs about Dissolved Carbon Dioxide in Captive Marine Systems

Related Articles: Carbon Dioxide

Related FAQs:  Dissolved Oxygen and Aquariums,

The Clown Trigger, Balistoides conspicillum. What can your livestock do if CO2 is too high? Swim away?

Low pH and outside air 1/7/10
Greetings to whomever is at the helm this day,
<BobF currently>
Now I know you folks hear this allot <parceling?> but it bears repeating, Thanks for the invaluable service you provide to those of us who keep fishies and their counterparts in glass boxes!
<Welcome! Siaynoq!>
I hope the questions I have today will be simple ones. I've had chronic low pH for a few months now. While searching for causes and solutions at WWM I believe I may have come up with some ideas on this. My home has a vent free gas fireplace so I'm thinking "this started at the beginning of heating season".
Unfortunately I live in the Northeastern US so opening a window is not an option at this time of year. I read here about pumping air in from outside. My question is, what kind of air pump do I need and where would I find such a pump?
<A good diaphragm type will do... I like the Tetra Luft line m'self. Just got to mount it where the rain et al. won't damage it>
My tank is adjacent to our solarium so I'm thinking that the plants take up CO2 and give off O2
<Mmm, the reverse at night... the "dark reaction"...>
and if just putting an air pump in that room would be sufficient. The solarium is heated by that fireplace I spoke of but there is electric heat backup and I could close the doors (although I'd prefer not to). Any thoughts on this?
<Mmm, well, you could mount this pump outside a window... I'd be checking your CO2 levels in the house... during the night particularly. Am concerned here>
I currently have no way to test for oxygen in the tank or out.
<Easy enough to do...>
Thanks much,
<Welcome. Bob Fenner>

Co2 introduction 4/30/09
Good morning think tank,
<Good morning Alex.>
Great service you all provide. I've read about CO2 diffusers and chambers. I was wondering if it's feasible to introduce the CO2 via pressure tank into the inflow line with a T tube and have the canister filter diffuse the CO2 through its media and back into the tank from the outflow or would the media absorb it too much?
<I see two potential problems with this setup. The first is that depending on the media, it may be absorbed, the CO2 in he chamber will create a more acidic environment, and the media used in it would have to both survive the pH. The second issue I foresee is that some media reactors are set up in such a way that the CO2 may pool in the top of the reactor. Commercially available CO2 reactors and Calcium reactors that experience CO2 input generally have a method of keeping the CO2 suspended in the water rather than pooled in the top of the reactor.>
It seems like an elegant solution.
<Please research commercially available CO2 reactors, and consider purchasing a reactor for CO2 to use separately from your media reactor.>
Thank you in advance, Alex.
<Your welcome, Josh Solomon.>

Re: Water quality... CO2... pH effect... more    1/8/09 Hello, <Hello Jim.> Per Minh's instruction I did the "Aeration Test". With exterior air the PH rose to about 8.3 from 7.9. <Did you also do the same Aeration Test with inside air? Did the pH remain the same or close to 7.9? If this is the case, then the air inside your home does contain excess CO2.> In my location it's too cold to open a window. How else might I fix this? <If increasing ventilation by opening a nearby window is not an option, then you may need to find another way to introduce outside air into the tank. One simple method is to run the air intake line from your skimmer to the outdoors. If your skimmer does not allow you to do this or if you don't run a skimmer, another method is to run one or more air pumps with their intakes connected to the outdoors. Lastly, another method is to increase your refugium's capacity to grow macro algae by using a stronger light (http://www.melevsreef.com/fuge_bulb.html) or adding another hang-on refugium. Using a fast growing macro algaes like Chaetomorpha will encourage increased CO2 consumption as they grow.> Thanks again Jim <You're welcome. Cheers, Minh Huynh.> <<RMF feels compelled to urge you to get/use an in-home Carbon Dioxide monitor... the accumulation of CO2 such that it affects the pH in our aquariums is of concern to our own health>>

CO2 Pollution Could Erase Coral Reefs | Wired Science from Wired.com   7/3/08 Should attach this to the CO2 articles J -- <D'oh! Will do. B>

New CO2 system problem, help!  11/18/06 I can't tell you how reassuring it is to know that you WWM folks are out there. Love your site! <Ahh, by your expression...> I set up my new Red Sea Pro CO2 system this afternoon, after buying a 22 oz "paintball" CO2 tank (the type it was designed for). I followed the directions to a tee, got things running at one bubble per second, then went out for about two hours. Upon my return, there were no bubbles going through the counter. Upon further examination, I realized that the tank pressure was zero, and that the tank was empty. I watched the guy at the shop weigh the tank as it was being filled. It felt full. More on that later. Particularly odd was that I had set up the kit's CO2 level indicator before I left. It was showing totally low when I left. When I returned and investigated, I refilled the indicator with a new water and reagent. After the ten minute wait, still nothing but the blue color that showed the same totally low CO2 level. Any CO2 I had is gone, but I have no idea where it went. <To the room?> I know this whole situation can't be right, but what I don't know is where and how to start troubleshooting the set-up. <Mmm... can be done (investigated) via low tech. to sophisticated methods... a spray water bottle to spritz around the gear (when the tank has gas in it) and all is operational, on/off may well show you where the leak is> I have only two clues to start with: 1) when I first screwed the regulator onto the tank, the pressure was only about 52 bar, while the "normal" range on the gauge seems to be 75 bar. <Mmm... well... a clue here... the pressure will be "normal" when there is much of any CO2 in the tank... only drops below this setting when the gas is "running out", i.e. getting low. Your tank may not have been filled much after all> 2) The reactor seemed to be making more noise, and putting out more and bigger bubbles (like a burp every 10 to 20 seconds or so) than I had expected from reading the manual, and thinking of tanks I've seen in shops. Help? <... Mmm, shouldn't "burp" at all... may be a sticky/faulty regulator at play here (as well). I would take the entire unit back to the dealer, have them trouble shoot it in front of you. Bob Fenner>

Low pH and Excessive CO2, and excessive algal growth 10/25/05 Crew, Scott Z. from Reefland.com. here, hope all is going well! I have a question regarding low pH and excessive CO2 and their effects on nuisance algae (that is the growth of, not elimination of). I have seen reference's over the years that low pH and/or excessive CO2 can increase the growth of nuisance microalgae. I, however, have never seen any details regarding this. For example, if one's pH is terribly low (5 hours after lights on, pH is at 7.8) can this be the sole cause of nuisance algae growth absent any "alarming" NO3 or PO4? <Can be a significant contributing influence/factor> And obviously the algae is a consumer of CO2 but would excessive amounts be a sole contributor to an "outbreak"? <Not hardly ever, but yes... sometimes> My questions come from an outbreak that I had not long ago which occurred shortly after the addition of a CA Reactor. Nitrates and Phosphates are undetectable (likely from the algae consuming any traceable amounts that were present prior to the addition). Prior to the addition of the reactor and the following outbreak, PO4 was undetectable and nitrates were <10ppm. I have no vegetable filtration (which I know would help) so I increased frequencies of water changes to 10-15 gallons per week (in a 75-gallon) and although it has drastically helped the pests it has not totally eliminated it. Before I move to more drastic measures to finally rid the rest of it, I want to get past the thought that the reactor (and subsequent low pH and CO2) is a contributing factor.  Despite all my best efforts to increase the pH (nightly lows 7.6 to daytime highs of 8.0) with Kalk and additional aeration, and with the comments I have read, I can't get over that this may be part of, if not the major contributor of, the nuisance algae encountered. These included Bryopsis, Derbesia, Valonia and an unidentified brown wafer type algae. Thanks! Scott Z. <Likely these have become entrenched, are poisoning other photosynthetic life/activity, modifying the environment for their own ends... The best route would be to go with veg. filtration as you mention, a DSB, chemical filtrants... and biological controls. Bob Fenner> 

Knop C calcium reactor Hello WWM crew, I recently bought a Knop C calcium reactor and it seems to be missing the tube to feed CO2 to the bubble counter. Can I use a clear vinyl tube (bought from Home Depot)? It says it can be used for "gases" and can handle 55psi. Thanks in advance and keep up the great work. Sincerely, Aldrin <Mmm, am concerned re the CO2 "getting loose" here... you can likely use this vinyl tubing... but the more pressure resistant and carbon dioxide resistant (blue) tubing) is better, less likely to lose secure attachment, degrade with exposure. Of all people, my wife (Diana) used to distribute Knop in N. America and still has some of this tubing. If you'd like to contact her, she still maintains the knopproducts@hotmail.com address. Bob Fenner>

Re: Knop C calcium reactor Thanks Bob. I will be contacting Diana and see if I can have her send me a foot or two of the blue tubing. I set up the reactor last night with the vinyl tubing. Pressure dropped from 20 PSI to 18-17psi this morning. There's definitely some CO2 escaping somewhere. <Yikes... do leave some windows open, turn on, check the battery on your home carbon dioxide monitor... Or better still, turn off the unit. Bob Fenner> Thanks again. - Aldrin

- CO2 Refills - hi could you help me, do you know where I could get co2 bottle refilled? yours sincerely p Rolfe <At any welding or gas supply house. Praxair is a national chain that you might seek out in your yellow pages. Cheers, J -- >

- Excess CO2 is In the House - Hello, all.  I need to pick your brain again, if you don't mind. I've been having low pH problems for some time.  I've discovered after reading through your FAQs and doing some experimenting, that I have an excess of CO2 in my house. <Are you basing this simply on depressed pH or testing? What else have you done to address the pH? You realize that it is the natural tendency of marine systems for their pH to drop, and it's only rarely caused by CO2 build up in the house and then most often in the winter when homes are shut tight.> I've been trying to keep my windows opened as much as possible, but the weather hasn't been cooperating.  Even opening them an inch lets some of the rain in.  I was hoping to find a more permanent solution.  I saw through the FAQs that some people use outdoor air pumps to pump air directly into their tank.  Unfortunately, I'm not sure this will work in my case.  The only area in the back of my house that I could place a pump has too many possible pollutants (e.g., propane grill, dryer vent).  I also found one mention of a "heat exchanger", but I'm not sure what this is or where to find one.  Can you tell me what this is? <I'm not sure, given the lack of context... heat exchanges come in all shapes and forms - refrigerators and air conditioners are technically heat exchangers. Not sure how one would be applied to this situation.> Can you suggest other ways of venting the excess CO2? <Really, getting fresh air into the house - if this is really what your problem is - is your best solution.> My tank is in the basement.  I'm planning at some point to have a bathroom put in down there.  Would the bathroom fan be enough to vent the room? <Hard to say, but probably not much - bathroom fans typically pull air out and vent that air outside... without a source of fresh air from outside, this fan wouldn't do much for you.> I have another problem that may or may not be related to my low pH.  I have an AquaFuge 24 refugium with Caulerpa in it.  By all accounts, this algae should be growing out of control, yet I haven't had to prune it in months.  It does grow, but very slowly. <Doesn't really follow that you have a CO2 problem then... excess CO2 in your water would cause this stuff to grow like crazy.> I have a 32-watt power compact lamp on it.  I've seen references on your site of people that have 64-watt lights on them.  Is 32-watts enough? <Should be plenty.> Another possible problem could be my pump.  I'm using the original Rio pump, which may not be providing enough water flow.  I get a film of slime algae on the top of the water that blocks the light.  I try to keep it scraped off, but it grows back quickly.  I don't mind upgrading to a stronger pump, but I'm not sure which one to get.  I want don't want to get one that is too strong for my 'pods to grow.  Is there a GPH that you can suggest that will give me the best of both worlds? <Probably a good question to pose to CPR, as in how much flow is too much, but I've run this device with a MaxiJet 600 with no problems... could start there.> I'd like to switch to Gracilaria, which would also benefit from faster water flow.  I've been hoping to get rid of the Caulerpa, but I figure if I get it to grow well, I'm not likely to have much success with something more demanding. Thanks, Patrick <Cheers, J -- >

- Excess CO2 is In the House, Follow-up - Sorry if I was too vague, but I was trying not to write a book.  :-) <Understood.> I'm assuming that I have too much CO2 because when I opened my windows for about 10 hours, my pH jumped from 8.15 to 8.3.  Normally, my pH ranges from 7.95 to 8.15.  Even with my dKH up to 14, my pH never gets above 8.15.  If I shut my calcium reactor off for the day, I can sometimes get as high as 8.2, but then of course my dKH starts to go down. I don't know if this helps, but the "heat exchanger" I was referring to is on http://www.wetwebmedia.com/marphfaq2.htm under the heading "High Alkalinity & Calcium VII". <Yeah... I read this and went as far as to speak with Anthony about what this device might be, but we're both at a loss to explain its utility. I was hoping there was some device that I could install that would automatically exchange more outside air for me.  I don't know if such a thing exists. <Probably poking a hole in the side of the house and adding a fan - other than that, you'll have to get a window open, perhaps throw a towel on the floor so the rain doesn't destroy everything.> My Caulerpa has been growing better since my CO2 problem started, but still not as fast as I would expect.  I think it may be that I have too much slimy nuisance algae in my refugium. <Yes, would be a competitor for nutrients.> I'll try cleaning it out to see if that helps. <Yes, and increase circulation within the tank, this will help.> Thanks for your help. <Cheers, J -- >

- CO2 Supply - Can I outfit my 20oz CO2 paintball cylinder and use it for my plant aquarium? <You could, but think there would be two major issues: first, finding a regulator for it and second having to refill it quite often. Seems a better and more economical solution to pick up a five pound tank and go the standard route. Cheers, J -- >

- CO2 Injection for a Reef Tank - Good day. <Good morning.> I have been admiring your website for quite some time and I now may have a question worthy of asking you. I noticed that the area of FAQ's under dissolved oxygen  ( http://www.wetwebmedia.com/dissolvedoxygen.htm ) is empty so you may want to put this in there as it may apply. <Ok.> My question relates to adding C02 to my reef tank. <Why would you do such a thing?> If I bubble in C02 into the tank will the skimmer take it out by trying to saturate the water with another gas ( air / nitrogen and O2 )? <To a certain extent, but depending on the efficiency of the skimmer it likely won't get 100% of it.> I have a 110 gallon tall tank with an 80 gallon sump that has been divided for filtration and for macro algae growth to remove dissolved organics. I would like to inject C02 into the water to help with the macro algae growth (razor Caulerpa) I understand this will effect my PH so I would have to watch this closely. <I wouldn't recommend this. Should be sufficient CO2 from other organisms in the tank and also from the plants and corals during the dark phase. The presence of CO2 is rarely the limiting factor in algae growth but rather the other foods: phosphate, nitrogen, and potassium... [think fertilizer] which typically come from the tanks inhabitants.> I am currently looking into getting my calcium reactor going thus I may have some residual C02 in the effluent... <Usually not much... the residual amounts are typically used up very quickly by other processes, including your algae and also skimming, overflows, etc.> That may be enough to help the plants enclosed are some pics of my set-up ... I have been doing this " reef thing " for a good 10 years or so and there is still so much to learn, any comments will be appreciated. <I think the reason for slow algae growth is a lack of organics... you don't have much in your tank, and it's my guess that as a result you're not feeding much. I will reiterate, I don't think it is wise to add raw CO2 to your tank... the water will acidify and cause other problems - deplete your buffers, etc. Much better to add CO2 via a calcium reactor, where the 'reactor' will use most of the CO2. As for you the growth of your algae, I'd look to extended lighting and dissolved organics from fish/feeding to fill this gap. Give the system some time and I'm willing to guarantee that the algae will take care of itself, to the point that you'll be asking us how to get rid of it.> In the sump pic you will see a top fathom skimmer, this has recently been replaced with a modified version of the TF utilizing a air injection system before the impeller and a taller reaction tower. This modified skimmer pulls out some nice dry foam on a regular basis. The lighting on the sump is not shown either as this sump pic is an early one. I am running close to 100 watts of compact fluorescent light on the "refugium". I hope this question is worthy of your attention. Kevin
<Cheers, J -- >


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