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CO2 By Human Respiration


  1. Alternative source of CO2
    by (Paul Krombholz) (Tue, 18 Jul 1995)
  2. Aquatic Plants Digest V1 #195
    by (Paul Krombholz) (Fri, 21 Jul 1995)
  3. CO2 bubbly thing?
    by John Jensen <jjens/> (9 Feb 1998)
  4. Re:CO2 by breathing
    by krombhol/ (Paul Krombholz) (Fri, 29 May 1998)

Alternative source of CO2

by (Paul Krombholz)
Date: Tue, 18 Jul 1995

What with all the stories exploding fermenter bottles and rocketing CO2
tanks, you may want to consider another CO2 source---yourself.  You breathe
out two or three percent CO2 all the time, and it can be collected and
bubbled into the tank with an airstone.   I breathe into a plastic garbage
bag, and then pump the air into my plant tanks every other day.  The pH
typically goes down to 6.5 to 6.7.  One bag does 3 fifteen gallon tanks.
The CO2 is free, and you can't overdose your tanks, at least, I have never
seen any ill effects on livebearers and zebrafish.

Think about it!

Paul Krombholz

Aquatic Plants Digest V1 #195

by (Paul Krombholz)
Date: Fri, 21 Jul 1995

Hoa writes:

>You meant you were serious?  It seemed like such an inefficient way of
>injecting CO2, considering the low concentration of CO2 in your breath.
>It must be a very big bag of air you use.  How long does it take to fill it
>with your breath?  And you are not just injecting CO2, but O2 and N2
>(mostly).  How do you deal with undissolved gasses?  (I don't have the
>original posting anymore and I can't remember what you used for the reaction
>chamber.)  I'm sorry if I had offended you, but I thought you were joking.  
Yes, I am serious.  The method really works well.  From one four inch plant
I have produced,in two years, a bushel (I am not exaggerating!) of Anubias
nana which I sold for $80.00 at a tropical fish store.  They were grown
underwater in a 75 gallon tank.  It takes me 4 to 5 minutes to blow up a
bag.  I do it while stepping up and down from a chair to increase my CO2
production.  If it did it while sitting down, it might take 15 to 20
minutes.  A bag does three fifteen gallon or one 55 gallon, or even one 75
gallon tank for two days.  The rate of bubble production by the plants does
not seem to fall off until the third day.  I knew that using low percentage
CO2 works because I grew aquatic plants for my master's degree research
under algae-free (almost sterile) conditions in flasks, and I found that
bubbling the flask with 1% CO2 produced very rapid growth which was limited
by the light intensity, rather than the CO2 supply.  The method of delivery
is through an airstone.  I have an air pump enclosed in a small bag with
the electric cord and air tube coming out of one end.  I attatch the tube
from the big bag that I blew up to the other end and use the pump to empty
the big bag into my tanks.  I don't know the volume of the big bag, but I
can find out if you are interested.  The open end is bunched around a 1/2
in diameter tube and tied with rubber bands, and, therefore, the volume is
less than the value stated on the box.  I once had some dry ice, and I
threw some pieces in my 55 and let them lie on the bottom, bubbling away
until they were gone.  I was surprised how many pieces I had to throw in
before the pH got down to 6.5, which is what I get with my breath.  The O2
in the bag may be 2 or 3 percent lower than in atmospheric air, but I
havn't seen any ill effects on fish or anything else.  The N2 in the bag
should be essentially the same as that in atmospheric air, and so it should
not change the amount of dissolved N2 in the water.

It works for two reasons, I think.  One is that atmospheric air has .003%
CO2, and, if you increase it to 3%, you are increasing the concentration by
1000.  Since CO2 is fairly soluble in water, such an increase would allow a
big increase in the amount in solution.  The second reason is that a person
puts out quite a lot of CO2.  I read somewhere that a resting adult puts
out as much heat as a 100 watt light bulb.  When exercising, as I do when
stepping on and off the chair, the metabolic rate can be 10 to 15 times

 I wrote this up in the Aquatic Gardener back around 1991 or so.  I can get
you  the reference, if you are interested.

Paul Krombholz

CO2 bubbly thing?

by John Jensen <jjens/>
Date: 9 Feb 1998
Newsgroup: rec.aquaria.freshwater.cichlids,rec.aquaria.freshwater.misc,rec.aquaria.freshwa

Roland Tan <> wrote:

: How do you make co2?

: Is there a site to this?

I think someone already gave a one answer (sugar and
yeast produce co2 which is piped to the aquarium), but I'd
like to suggest an alternate.

I'd suggest a simple mouthpiece and valve combination, so
that anyone watching the aquarium may pipe his co2 to the

  #####             |               |
  |c .|             |     <(((=<    |     
  |   \             |               |
  |   ==={}=========|  }}       }{  |
  -| |-             |   }  {    {   |

Isnt' there a Japanese name for inventions that are once
practical and useless?


Re:CO2 by breathing

by krombhol/ (Paul Krombholz)
Date: Fri, 29 May 1998

Steve Pushak wrote:

How many tanks can you fertilize with a garbage bag full of exhaled air? How frequently do you do this? I presume that you are using glass covers on these tanks to retain the CO2 atmosphere? Do these tanks have any water circulation of any kind in them? I've always been concerned about blue green cyanobacteria if there is no water circulation at all especially with a newly set-up soil tank. Do you ever have problems with BGA and how do you deal with it in these small tanks?

The method was written up in The Aquatic Gardener 4(3) and TAG 4(4), but that was a long time ago. I can do three 15 gallon tanks or one 75 gal with one bag. With the tanks covered tightly with glass, it lasts about 2 days, and then the rate of bubble production starts to drop. I don't have any kind of water circulation at all and almost never get bluegreen algae take-overs. I don't think that CO2 additions encourage or discourage bluegreen algae. If the BGA gets bad, I just turn off the lights and wait until the snails eat it up. In poor light the algae becomes palatable for ramshorn or pond snails (or guppies) and they finish it up in a week or so.

This method of delivering CO2 is what I think of as REALLY DIY CO2, and, compared to a yeast culture, a person really cranks it out. Just resting, an adult is producing the energy equivalent of a 100 watt bulb. The CO2 is a lot more convenient to diliver if you have the air stones and air tubing for the tanks set up permanently and you just attach the bag of exhaled air to the pump and turn it on with a timer set to about 40 minutes, which is, for me, about the length of time it takes for the pump to empty the bag. The pump for delivering the exhaled air is in a small bag with a hole cut in the corner, and I stick the tube from the air bag into the hole and tie it on tight with a rubber band.


Ken Cova wrote:

.....I've noticed that if I fill my CO2 reactor (two upturned Rubbermaid containers in the sump) by blowing through an air line, my tank PH readings are lower than when I run with yeast generators. Is yeast CO2 less concentrated than "human" CO2?

Not necessarily. Exhaled air contains roughly 3.5% CO2. I don't know what the percentage is in the yeast CO2 reactors; it could be over 50%, but the amount in the tank is due to the rate that the mix gets bubbled into the tank. If you collected all the gas from a yeast reactor and pumped it into the tank with an air pump, you might get too much CO2 in and kill the fish. Exhaled air, on the other hand seems pretty safe. I have never seen it cause distress in guppies or zebra danios, which is all the fish I have.

Paul Krombholz, where our month-long drought was broken in dramatic fashion yesterday and today.

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