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Re: Aquatic Plants Digest V4 #1609 CO2 in Sump
Dear Greg,
I have a wet/dry on my 100 gallon tank. I inject CO2 via an Eheim diffuser
in the wet/dry. Initially, I had the diffuser in the half of the wet/dry
that held the bio balls. That made cleaning the top of the diffuser very
difficult so I eventually moved it to the sump portion of the wet/dry. I
have tight lids on the top of the wet/dry so that the CO2 that is not
immediately absorbed in the water stays trapped in the wet/dry to be
absorbed as the water tumbles through the wet/dry. What I have found
critical to maintaining high CO2 levels in my system is controlling the rate
of flow through the wet/dry filter. Even though I have the return spray
bars under water, if the rate of flow through the wet/dry exceeds a certain
rate, the CO2 is driven off very quickly. Surface agitation is one factor
that drives off CO2. With the return bars under the water that is not too
much of a problem except at maximum flow rates. However, in my system,
whether the water flows smoothly and quietly into the built-in prefilter box
or cascades loudly into the prefilter box makes a big difference in the CO2
level. Apparently, the water cascading into the prefilter box drives off
the CO2.
To control the rate of flow through the wet/dry I have a ball valve after
the Eheim 1060 hobby pump which I use as the return pump. The Eheim can
have its current flow restricted without any reliability problems. Not all
pumps are built that way.
By reducing the flow of water through the wet/dry I keep the water level in
the wet/dry at least 12" deep (which allows better absorption of the tiny
bubbles from the diffuser) and I also minimize the CO2 lost due to surface
agitation and prefilter tumble.
Try reducing your rate of flow. It works for me.
Best Regards,
Roger Gordon