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[APD] Re: Aquatic-Plants Digest, Vol 11, Issue 13

Sorry, guys.  I was relying on your knowledge of my post 2 days ago, let me see if I can be more clear.

First off, when I got home and found an inch or so of accumulated gas in the reactor, I shut the CO2 off completely, closed down the needle valve and let the Hagen powerhead run for 4 hours straight.  The lights went off eventually as it ran, and it ran for an hour in the dark.  The pH rose from 7.1 to 7.7.  The trapped gas level essentially remained constant.  The powerhead had no ability to evacuate it due to limited flow rate, and the gas did not dissolve.  This proves to me without a shadow of a doubt the gas in the reactor was NOT CO2.  Nitrogen?  Perhaps.  From partial pressure outgassing into the bubble or from contamination due to impure CO2 supply?  Can't say for sure, but it seems to increase non-linearly (accelerates) over time which makes me think Paul is right, and my CO2 cylinder is not necessarily contaminated.  Hard to prove, though, isn't it?  I mean, without actually analyzing the cylinder contents, I can't "prove" the contents are pure.

The second part has to do with the filter causing extreme outgassing.  I have a Fluval internal filter in the tank that moves _lots_ of water.  (You know, maybe I should have just tried to rig this thing's outlet through the reactor?  It has incredible flow- the Hagen powerhead can't touch it).  It created strong surface current because the outlet in the upright position was barely an inch under the water surface.  In a previous post I mentioned going home and laying it down to try to reduce outgassing by lowering the outlet point.  (If 60 bpm won't get me 25ppm, and Scott can get 30ppm with 12 bpm in the same size tank, then I have an outgassing problem of Very Large Proportion.)  And so it was, I laid it down, and suddenly, the pH drops a full point in very short order, the solenoid cuts off and stays off for an extended period of time before the pH rises enough to trigger more gas.  Outgassing problem solved.

But the gas bubble accumulation is not solved.  It still accumulates, and I have to burp it manually a couple of times a day, which is a major pain. That is why I think for now I'll just use the diffuser instead of the reactor, it's so aggravating that it can't be left alone for long.  But I may try to Rube Goldberg the very strong filter output into the reactor to see if that will blow things out enough to keep the "air" from accumulating.  At least if it works, I will know how to rig things when it all moves over to the larger tank.


from Scott:
"You'll use more CO2 to maintain CO2 levels in your tank
with a diffuser than with and airstone like the Eheim.
There's a reason your reactor isn't working right for you
and solving that issue will do more for you in the long run
than then an airstone -- jsut my 2 pennies.

I'll guess that your were shedding CO2 so fast that you had
to try to inject it so fast that the reactor couldn't keep
up. Tame your tank as far as shedding the CO2 goes, turn
down the CO2 injection rate accordingly, and you'll have
good CO2 levels, no buildup in the reactor, and virtually
100% absorbtion of the CO2 into the water.

As for sumps, if your aquarium is already sloughing a lot
fo CO2, then changing to a sump won't make a big diff in
consumption -- It's sort of like, if you switch from big
pickup truck to an SUV, you won't get a big change in mpg.
However, if your set up is relatively efficient, then
changing to a sump can easily double your consumption or
more. At least that seems to be what the reports so far
have shown.

Scott H."

>From Dan:
"I'm having trouble understanding. Can you clarify? Was the trapped gas from
impurities in the CO2 tank, or from the partial pressure effect, or what?
What do you mean by 'I dropped the filter down sideways, and the gas
consumption dropped...'?

Dan Dixon"

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