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Re: [APD] Re: Bubbles? -- or - Can sumpin' be Jumpin' Jack Flash?

--- Andrew Mitchell <andrewm at cse_unsw.edu.au> wrote:
> On Wed, 2004-02-04 at 02:35, S. Hieber wrote:
> > Depending on how it's done, it seems that a Trickle
> filter
> > will not, or at least need not, cause all the CO2 to
> > escape. While my experience was an increase in CO2 use
> of
> > about double, George Booth has reported results much
> In George's article where he reports his experiments,
> . . . I did some calculations on what this worked out as 
> a
> couple of years
> ago . . .I think it
> was well over 1
> bubble/sec (of the size of bubble that I use), which
> would still be much
> higher losses than you suffer from. Perhaps your
> cannister method was
> just extremely efficient?

If that's right about George's rates -- I haven't read that
particular stuff on George and Karla Booth's excellent web
site in a few years -- then yes, he was using more CO2 and
getting less of it into the water than I ws with the
canister setup. And the reason was that the  canister setup
was very efficient with CO2 -- 10 pounds would last over 5
months on a tank twice the size of George's. If I'm reading
this right -- it pays to double check the math. If you
start off great, you have more to lose -- sounds like
something from Laotzu ;-) .

> Looking at David's figures . . .
> his losses are
> about 5 times your losses. Perhaps he should consider
> sealing his sump. . .

I think you only have to cover the trickle side--CO2 is
heavier than air and wwants to go down not up, as I recall.

> I've read/heard that there can be a large loss in the
> overflow itself,
> which increases the partial pressure of CO2 in the
> overflows (and
> perhaps between the water and the lids).

That would be my guess on where the loss occurs if teh
trickle chamber is covered. 

> Whilst I use a
> method (which I
> will write up some day) that virtually eliminates this
> particular issue,

You mean CO2 loss in the overflow? I'd like to hear it. I
hope it doesn't involve impeding or reducing the drain --
an oversized drain is the safety against an overflow
becoming over-the-edge --literally ;-)

>> I have tried it, briefly. My early results were
> inconclusive... my sump
> is not perfectly sealed and I was worried that the
> positive CO2 pressure
> may eliminate too much O2 pressure from the sump,

I don't think it would; the pressure is only a couple of
psi at the very most, no? The only containment is the
weight of the water on the sump side, which can rise and
fall a bit. And the water is always bringing in more O2 --
so I think you'd get a CO2 rich gas mix but not O2 less.
And on a planted tank the biofilter isn't doing the main
work anyhow so there's lots of room to wiggle.

> suffocating bacteria.

Oh, they're tenacious little buggers. I have a lot of faith
in them.

> Sure th water would then leek O2 into the sump, but how
> much if the sump
> is pressurized?

Hmmm, see above :-)

> My other concern of a well-sealed sump  was that in the
> event of a power
> failure the water level would rise faster in the sump
> (due to the
> trapped air) and spill. 

It will drain your tank until you get below the "air break"
(where the output is in the water) or the overflow lip. The
former is usually the worst case. IN any event, I think a
quality check valve is a must on an "open" system like a
sump or wet/dry set up.

> I am particularly careful about
> avoiding spills . . .
> Hence I refuse to seal
> that part of
> my sump. (yes, my sump does have an overflow to the
> garden, but not
> quite fast enough)

Thus, why the drain is always bigger than the faucet ;-)

But seriously, either the 60s are revisting my grey matter
or I'm just missing something here. Wouldn't gas pressure
in the trickle chamber in the wet/dry, assuming it was
greater than I believe it is, wouldn't it deter water from
coming into the sump? I don't think there's any need to
cover the "sump" side (as opposed to the trickle side) of
the sump. There's no surface agitation on that side, so the
CO2 isn't going to race out. I'll bet a change in water
temp of 1 or 2 degrees will have a bigger impact on the
amount of CO2 that's in the water. Guess someone should
double check *that* math -- but I recall Karen Randall
making the point with numbers that temp has a significant
impact on the amount of CO2 in the water.

fun stuff, no? 

Scott H.

S. Hieber

-  -   -   -   -   -   -   -
Amano Returns
to the AGA Annual Convention
Nov 2004 -- Baltimore

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