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Re: DIY CO2 systems

No worries about getting a little bit of the yeast culture in your tank,
especially if it was just mixed up.  Getting a lot of it in there after it's
been fermenting for a while could lead to alcohol problems with the fish.
If the mixture went thru the airstone, it could clog it up tho.  The check
valve, as you have it set up is a good idea.

You should be able to see results very quickly.  On the second or third day
a new yeast culture should be giving you a steady stream of CO2.  A couple
of hours after lights-on you should see oxygen bubbles coming off your
plants, especially where they are broken or injured.  My tank reminds me of
snow flurries in reverse sometimes, there are so many tiny streams of
bubbles coming off the plants.

I've been doing some experimenting (well, actually fooling around) with
yeast culture, and that's what it is, a culture, just like infusoria or
green water or BBS.  My current method is to keep a 2 litre bottle filled to
just where the sides begin to curve in.  I use a RedStar Flor Sherry yeast.
I think a champagne yeast would be just about as good.  David Logsdon of
Wyeast had this to say on the subject of yeast for CO2 generation-

"The best strain we probably have is the #3347 Eau de Vie yeast. It ferments
sucrose very well, and is clean in the aspect of esters, sulpher and other
fermentation biproducts. And is very alcohol tolerant, which is the other
aspect to consider."

I add two cups of sugar, 1/4 teaspoon of baking soda, a few drops of trace
element mix and one tetra initial stick.  I have yet to subject any of this
to scientific method, but this combination is working very well at the end
of it's second week with no sign of slowing down.

Previously, I used the very traditional bakers yeast and baking powder, then
a combination of bakers yeast and Flor Sherry yeast with a trace element.
Neither was entirely satisfactory.  They both went great guns for a few days
and then hobbled along getting slower and slower.  The straight Flor Sherry
strain with fertilization has had a fairly steady output from beginning
until now.

One thing I often see written as SOP, which I see no need for, is starting
completely over when the yeast peters out.  My method has been and will
continue to be waiting until the yeast culture shows signs of weakening,
then shaking it up, dumping out 3/4 of it, and refilling the sugar and
fertilizer.  As long as everything is clean and the yeast culture is still
viable, this works very well.  The bottle begins pumping CO2 again in a
couple of hours.  It is possible that occassionally the culture will get
invaded by some bacteria or wild yeast strain and have to be started over,
but I feel that this is less likely using the Flor Sherry or champagne
yeast, which has a very high alcohol tolerance.  A healthy culture of one of
these yeast strains, provided with all the necessary nutrients and enough
sugar shouldn't begin to decline until it produces enough alcohol to reach
it's tolerance level.  Little else could survive at that level.

Another point to consider is something that homebrewers refer to as 'stuck
fermentation', when fermenting (CO2 production) stops for no apparent
reason.  One fix the homebrewers use is to aerate the mash.  Sometimes they
go so far as to stick an airstone in the mixture.  If you've ever seen one
of the orange carboy caps that homebrewers use, it has two nipples, one for
the airlock and another for an airline.  Often tho, it is a simple matter of
shaking up the mash.  That can be very difficult if you are trying to make 5
gallons of wine in a glass carboy, but it's a simple matter for us.  If the
CO2 production stops for no reason, unscrew the cap, put a solid cap on and
shake it up real good.  Take the solid cap off immediately after shaking, or
the yeast may take it off for you!  If CO2 production doesn't start within
24 hours, it's definitely dead. I sometimes give my bottle a little swish if
I happen to be working near it, not enough to run any of the mixture up the

Another point is on sugar.  I never see any complaints about the price of
sugar so it may not be a concern for anyone. Brewers yeast, while it seems
to do a fine job of fermenting sucrose (cane sugar), was originally selected
and intended for its ability to ferment fructose (wine yeasts) or
maltose(beer, ale and barley wine yeasts).  Actually, just about any sugar
can be used.  If you find a cheap source of molasses or fruit juice that
hasn't been chemically treated to prevent fermentation, these will do you
just as well as refined cane sugar.  Note tho, in the case of raw juices
that haven't been cooked and canned, it is advisable to boil them first.

I think one of the limitations on using yeast for CO2 generation has been
traditional thinking.  Everyone has been using yeast, cane sugar and baking
powder because that's what's always been used to make yeast generate CO2 to
leaven bread, right? Wrong.  Right but wrong.  The idea in baking or brewing
is to have yeast do its thing and not leave any foul taste behind.  I,
personally, have no intention of drinking what's left in bottle after the
yeast is done with it.  This leaves me totally free to add anything that
will make yeast healthier, stronger and longer lasting, regardless of how it
taste.  That's what lead me to throw in fertilizer meant for aquarium
plants.  I have yet to come up with scientific proof that it does any good,
it certainly hasn't done any harm.  But I am limiting myself again, by
trying to improve the yeast culture using only what the aquarist has at
hand.  Who knows, 1/4 teaspoon of Miracle Grow might make all the