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Re: What are the risk of yeast seeping into water?



Chee Ming sent me some pictures of his in-tank yeast generator. He has
gotten some good plant growth but I'd still advise extreme caution.

"What I'm worried
about is that yeast might react with my plant nutrients rendering it useless
for plant use. Will it?"

The short answer is no, yeast cells in the water column won't have any
effect on the plant nutrients present. Yeast cells are everywhere in
nature - the only difference here is in the total number of cells which
could be present (several orders of magnitude more, no doubt).

The long answer however, really has more to do with the other product of
yeast fermentation and what it can possibly do to your setup. Yeast is used
in both baking and brewing. The growing yeast cells use sugar to produce
alcohol and carbon dioxide:

    Sugar     + Yeast =     Alcohol     + Carbon dioxide
C6H12O6 + Yeast = 2(C2H5OH) + 2(CO2)

By placing your generator in the aquarium, and depending upon the pressure
of the produced CO2 to keep the liquid inside of the bottle separate from
the water in your aquarium you are playing with fire. As you have already
discovered when you shook the bottle, sooner or later the stuff inside the
bottle is going to get into the water column of your tank. The yeast cells
are the least of your worries.

The sugar in the mixture can not only serve as food for yeast, bacteria of
all types like it too, including all of the bacteria inside of your
aquarium. Bacterial blooms can deplete the Oxygen in the tank very quickly
and will cut down on visibility. The alcohol in the mixture, even though
there isn't likely to be much, is not going to do anything good for your
fish or anything else in the tank which is alive. That is what eventually
stops CO2 production in most DIY yeast method CO2 generators - the alcohol
eventually kills the yeast cells off long before all of the sugar has been
converted. Fish don't benefit from a "cold one" at the end of a long day of
swimming around the aquarium. The alcohol would act as a poison, stressing
and potentially killing the fish.

External generators might be ugly, they might take up space, but they are
far safer for the health of your aquarium than the setup you are currently
using.

James Purchase
Toronto