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Re: [APD] CO2 and pH control

Scott wrote:
I don't think any of these results, by George, Dave, etc.
are bogus -- I don't even think they are inconsistent.
However, I think I might disagree with the conclusions that
some have drawn. I think the results show that sumps are
not *generally* the most conservative when it comes to CO2
*and* that some canister set ups can be as inefficient as
some sump set ups.

I tend to rely of my own experience when it comes to what CO2 setups work
and don't work. All that is easily done with a pH monitor.

Unfortunately, IME, the solution to an inefficient wet/dry CO2 setup has not
been simply "turning up the gas." There was a downward limit to the amount
of pH reduction I was able to achieve with a wet/dry, no matter how much gas
I bubbled in or how much I lessened the water agitation to lessen
offgassing. The ONLY way I was able to get pH into the mid 6s with a wet dry
was to allow my KH to get dangerously low (2 or less). A KH of 4-5 is my
comfort zone, and at that level I couldn't get lower than 6.8. I was using
two Aqua-medic Reactor 1000s, each with a Rio 1700 pump. These reactors are
rated each for tanks up to 500 gallons. I had two of these on a 240 gallon.

Remove the wet dry, plumb in two Eheim cannister filters, and shazam, the pH
control issue disappears.

Regarding canister filter injection efficiency/inefficiency:

I couldn't agree with you more on that, Scott. Canister filters with media
baskets can allow tremendous gas bypass. Even if the baskets seem to make
physical contact with the sides of the filter itself, gas can get by. The
only canister filters I have found that have the media in the filter without
baskets, basically stacked on top of each other in contact with the filter
walls, is the Eheim Classic Series. The 2217, 2215, and older 2213 filters
do not use media baskets, so the ceramic prefilter noodles, sintered glass
biomedia, and the loose filter floss (especially this after is gets muck in
it) all act like a big plug for the CO2 and keep it in the filter longer
than you would see in a cannister filter with media baskets, so more gas
dissolves into the water.

I have no idea of the relative efficiency of canister injection, but I'd
guess the Eheim Classic Series is the most efficient.

We all know that the name of the game with CO2 is water contact time. I
would think the most efficient way to get CO2 into the water is with an
in-tank reactor.

Eheim Classic canisters area nice choice for me because I don't like the
maintenance required for an in tank CO2 reactor and I don't like the
presence of the reactor in the aquascape itself. Eheim canister injection
requires zero maintenance, and I have never had an Eheim canister airlock on
me because of the CO2 I was putting into it. I would not use canister
injection if not for the Classic series. And I have been able to keep the pH
of my tanks where I want to using them.


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