co2 absorption time? - The Planted Tank Forum
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post #1 of 3 (permalink) Old 01-25-2007, 02:48 AM Thread Starter
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co2 absorption time?

If thats what you call it... Lets say you start pumping co2 into your tank at x seconds per bubble through a diffuser. How long do you wait before you test ph? Like how long does it take for that amount of co2 to level off so you can take an accurate reading? I'm looking at a 10gal tank for this question.

Also, when you test kh, the instructions say to "count the drops it takes to turn from blue to green" Does that mean drops overall? Or is that one drop to turn it blue, then how many subsequent drops to turn green? That one drives me crazy because it's a little vague to me.
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post #2 of 3 (permalink) Old 01-25-2007, 04:10 AM
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KH testing, and GH testing, at least with the API kits mean count every drop of reagent, including the one that makes the color change.

CO2 can't possibly show up all over the tank instantly just because we inject it somewhere in the tank. It has to circulate with the water all over the tank, reach equilibrium with the losses to the air above the tank, and build up exponentially to the overall equilibrium in the tank. If you use a pH controller, and have the needle valve open well beyond where it has to be to get to the concentration you want, the time will be the shortest. And, if you inject the CO2 in an external reactor in the filter return line, with a big flow rate filter, the time will be the shortest. For me it takes a couple of hours at least to reach the final amount in the water, but that is as measured at one location in the tank. Other locations will reach the final amount sooner or later than that.

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post #3 of 3 (permalink) Old 01-25-2007, 04:38 AM Thread Starter
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Thanks Hoppy!

Are you using that venturi reactor still? I switched from a limewood airstone to a rhinox style diffuser tonight and I would like to measure for changes in my ph (if there are any). Sounds like I should just wait until tomorrow, and adjust/test daily. If your using a reactor of some sort and I'm using a duffuser and filter flow, I'm sure I could add a few more hours to my time at least. I am backing down on my co2 though, so it's not like I'm starting from scrtach.
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