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Re: DIY CO2 for Wendell

Olga Betts <sae at arts_ubc.ca> wrote:
> Be careful about using the venturi intake on a powerhead for CO2 delivery.
> This can be powerful enough under the right circumstances to suck all the
> yeast mixture into your tank... no good... kills all the fish and means a
> complete tank clean. Better to run the CO2 through the impeller of the
> powerhead. If you sit the powerhead on a sponge filter, make a hole in the
> lift tube under the powerhead and insert the CO2 line there. This works
> perfectly and the powerhead will pluse a jet of very fine bubbles. Also
> running the CO2 through the impeller gives the CO2 a longer time and more
> thrashing about into order to dissolve into the water.

I disagree with the comment about the powerhead venturi being strong
enough to create a vacuum strong enough to siphon yeast water into the
tank. Yes, yeast water can be quite fatal to fish and plants. The two
guys here in Vancouver who had yeast diasters were NOT using the venturi
approach (inspite of my recommendations to do so). They were injecting
the bubbles into the fibre filters which were connected to the inlet of
the powerhead. These inlets had been drilled and sealed so that inlet
pressure was being applied to the interior of the yeast bottles. After
time these filters become plugged up and a high vacuum is developed at
the inlet of the powerhead. This vacuum IS STRONG enough to cause a 2L
plastic reactor bottle to crush and to siphon yeast water into the tank.

I repeat that I have NEVER heard of an incident involving a yeast
diaster when someone is using the venturi injection method. With the
venturi injection method, the vacuum decreases when the flow rate
decreases when the filter plugs. This is the OPPOSITE of the effect when
injecting at the inlet. This means that the system is stable (safe)
under normal powerhead degredation.

If someone would like to conduct a simple experiment, connect a tube and
empty 2L bottle to the venturi of a powerhead and observe if the vacuum
is sufficient to crush the jug. If so, repeat with the bottle half full
of water. I have not tried so I don't know. An empty bottle is much more
likely to crush than one partially full of water. A given pressure
difference on a larger area creates a proportionally larger crushing

I think this is an important issue to bring to people's attention
because of the potential costs of a yeast disaster. You can potentially
loose the majority of your fish and plants if not treated promptly
(within hours) and correctly (immediate strong aeration, add clarifying
agent and filter with micron or diatom type filter).

Steve Pushak                              Vancouver, BC, CANADA 

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