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CO2 by breathing

Paul Krombholz wrote in the APD:
> Roger Miller wrote:
> 
> .....CO2 is only about 0.03% of "normal" dry air, and water in balance with
> air will contain only about 0.42 mg/l of CO2 at 25C (about 77F).  That
> number drops noticably as temperatures increase.  A concentration of 20
> ppm CO2 is 48 times the atmospheric balance point; it's what the water
> would balance at if the air contained about 1.4% CO2......
> 
> This is a good time for me to give a plug for my method of delivering CO2.
> The air we exhale in normal breathing is between 3 and 4% CO2, which is
> about twice the concentration that would provide 20 PPM.  All one has to do
> is to exhale into a bag and then arrange to pump it into his or her tanks.
> Just sitting here and reading the daily APD is enough time to fill up a bag
> that can get the level up to 30 PPM in a 75 gallon tank.

Hi Paul,

I'm curious about your CO2 fertilization method which you do by
breathing into a garbage bag and then pumping the air into a tank or
tanks.

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 reason that I'm asking about this is that a friend and I have set up
two 15 gallon containers with potted Crypts and Swords which are the
excess from a bulk order which our local Vancouver aquatic plant club
made. Presently we have air stones in the tanks to stimulate the
circulation, oxygenate the water and prevent the formation of BG algae. 

The soil which we used is subsoil with virtually no organic content and
we added 1/4 by volume of sphagnum peat moss and then covered the pots
with a half inch layer of ~1 mm sand. We also added a little micronized
iron to the soil although I think it has plent of iron since it has a
rusty color and came from some veins of subsoil which obviously had iron
water leaching into it. The subsoil is a sandy silt with a relatively
low clay content.

At present we have fertilized with Ca, SO4, K and Mg in solution. We'll
probably fertilize with NPK in clay pellets once the roots have a chance
to get established. There may be some P available from the subsoil but I
don't know how much to expect. We chose subsoil because of its low P
content.

I use this air stone method of providing ambient CO2 into another
lo-tech aquarium that I have which gets about an hour of partial
sunlight a day (depending on cloud cover). The plants in this aquarium
grow very slowly but there are no fish and no fertilizer additions to
the substrate so I think it is N and P limited. 
Back to the holding tanks with the air stones. We have a plentiful
supply of bottled CO2 but these containers are a little small for
powerheads or other circulation devices. We could cover the tops with
plastic wrap and fill the airspace with CO2 from a hose system. It would
be nice to maintain some method of water circulation in the tanks (one
of which is a plastic utility tub). Currently the lighting on these is
provided by two 3' T-8 tubes however we have the option of putting a MH
lamp over the set-up or making some other adjustments. I'm not eager to
increase the lighting too high since one of the Crypts is C nurii and
all of the specimens of C nurii which I have planted in my large tanks
is melting. This Crypt seems to be more prone to melting than other
types of Crypts.

You mentioned that large CO2 additions without lighting increases also
seem to cause Crypt melting so I'm a little concerned about over
fertilizing by CO2 if we saturate the small space of air with CO2 and
then seal it. Bleeding air in from a tank will be faster than blowing up
a bag but we need to guesstimate the amount of CO2 we're adding...

Maybe all we need to do is tape the cracks on the window, close the door
to the room with all the aquariums and the CO2 cylinder feeding them and
breathe deeply! ;-)

Input and suggestions welcome.

Steve Pushak                              teban at powersonic_bc.ca 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!