Re:CO2 DIY idea

[Paul Krombholz <krombhol at teclink_net>]

    * From: Andrew McLeod <thefish at theabyssalplain_freeserve.co.uk>

.........Another (potentially) cunning plan...
Yeast in aerobic conditions, like most life, reacts sugar+oxygen--
CO2+water, which would actually be preferable as alcohol poisons 
yeast, and since alcohol is not entirely oxidised, the aerobic 
reaction produces significantly more CO2. However, it does not result 
in an increase in gas pressure, so it would only produce a CO2 
enriched atmosphere, and not produce a flow of CO2 like an anaerobic 
reactor, but since (I am assuming) CO2 is more soluble than O2, a 
flow of water through the reactor or an air pump pumping very slowly 
from the reactor into a diffuser might allow CO2 enrichment.

I have had a similar idea like this for a year or so.  My idea was to 
have a two or three liter soda pop bottle filled about 3/4 full with 
loose topsoil. The bottle would be stoppered with a two-hole rubber 
stopper and glass tubing would pass through one hole down to the 
bottom of the bottle.  Air would be pumped in through this tube and 
pass through the soil and then go out a short glass tube in the other 
hole which would be connected to air line tubing that would send the 
air into the aquarium.  Basically, the design is meant to circulate 
air through the soil and then into the aquarium.  For CO2 production, 
I would mix into the soil a tablespoon or so of uncooked, dry 
oatmeal.  An aquarium air pump would push the air through the soil 
much too fast, and and the percentage of CO2 in the air being pumped 
into the aquarium would be way too low.  To reduce the rate of air 
flow, I would put a piece of glass capillary tubing in the line going 
to the bottle.  This is glass tubing that is very thick walled and 
has a very small diameter canal down the center similar to that of a 
glass thermometer.  You can get it from scientific supply companies 
with a variety of capillary diameters.   With the right capillary 
diameter you should be able to get a flow rate that would raise the 
CO2 content of the aquarium considerably.  You don't have to use 
yeast with this set-up.  The fungi and bacteria and all the other 
critters in the soil will do the job.  When CO2 production wains, 
just mix in some more oatmeal.  (If you don't like oatmeal, you can 
use cream of wheat.  Basically, anything starchy will do.)  This has 
the big advantage, as Andrew pointed out, that the aerobic breakdown 
of the oatmeal is much more efficient at producing CO2 than anaerobic 
breakdown, and you don't have to worry about alcohol or other 
metabolic byproducts poisoning the system.

Somebody ought to try it.  I haven't bothered because it is easier 
for me to breathe into a plastic bag and then pump the contents 
(about 4% CO2) into my tanks.
--
Paul Krombholz in sunny central Mississippi