# co2 question



## geezer (Jun 7, 2006)

Hello all 

I got a silly question about co2 levels in my tank. The KH is 8, and when I wake up the PH is 7.5. co2 level 7ppm.

I do a rate of 130 bubbles a minute and by the night is over I get it around 6.9-7.0 PH, which gives me between 24-30ppm co2.

Does that mean I'm not getting the right co2 because it only reaches it within the last hour?

Do I crank it up so it reaches 6.9 PH, and then reduce the bubble count?

Or keep it how it is and work down the low PH?

unsure on how instant the PH must drop, or how long I should take before reducing
Confused


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## BryceM (Nov 6, 2005)

I'm not really sure about what you're asking. Do you run the CO2 24 hrs a day or just during the day? Most people recommend turning off the CO2 about 1 hour before the lights and turning it on about 1 hr before.

I'm lazy and run both the CO2 solenoid and the lights off of the same timer. Like you, I get the lowest pH at lights-out. By morning it slowly drifts upward, but not by much. I have almost no surface movement and a very tight lid.

Also, I'd ignore the pH/CO2/KH chart. It just doesn't work that well. Take a water sample from your tank and aerate it for about 12 hours to drive off all the CO2. Then check the pH. Subtract 1.0 units from this and that should be your goal for the aquarium.


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## ex0dus (Mar 14, 2006)

guaiac_boy said:


> I'm not really sure about what you're asking. Do you run the CO2 24 hrs a day or just during the day? Most people recommend turning off the CO2 about 1 hour before the lights and turning it on about 1 hr before.
> 
> I'm lazy and run both the CO2 solenoid and the lights off of the same timer. Like you, I get the lowest pH at lights-out. By morning it slowly drifts upward, but not by much. I have almost no surface movement and a very tight lid.
> 
> *Also, I'd ignore the pH/CO2/KH chart. It just doesn't work that well. Take a water sample from your tank and aerate it for about 12 hours to drive off all the CO2. Then check the pH. Subtract 1.0 units from this and that should be your goal for the aquarium.*


Would you mind explaining the bolded a little better. By the sound of it, I like your way vs the ph/kh charts. So you take the tank water, let it sit in a bowl for 12 hours and then read the ph. Then you minus 1 unit of ph and that is your target range. Did I understand that right? How accurate is this and will it dose @ 25-30ppm co2 in my tank?


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## geezer (Jun 7, 2006)

so really I wanna be aiming to go down a full point on the PH chart?

i.e 7.5 to 6.5 (after testing the water of course)


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## John N. (Dec 11, 2005)

Yes that sounds about right. Shoot for a pH of 6.5. Watch the fish to see any stress or surfacing. If they are, then crank back the CO2, if they aren't then your probably can inject more CO2 to ensure a high CO2 level.

The pH should drop in an hour or 2 once the CO2 is flowing.

-John N.


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## BryceM (Nov 6, 2005)

Yep. If your "degassed" pH is 7.5 then shooting for 6.5 should give you good results. There is some debate about the "actual" CO2 concentration with this method since the concentration of CO2 in degassed water is hard to know with certainty. In any case, a pH drop of 1.0 units means that you have increased the baseline concentration by 10X. This probably puts you in the neighborhood of 30ppm.


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## ex0dus (Mar 14, 2006)

So as I make my ro water and add the baking soda and equalibrium, I should let it sit for 12 hours then read the ph. Then on the controller dial it down a full unit of ph from what it read in my bucket?? That seems alot easier than testing, testing some more and when i think im done test some more.


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## geezer (Jun 7, 2006)

it takes me about 4 hours to reach 7.0. i cranked it up now but the bubbles seem to come out a bit big from the red sea co2 reactor. i'm hoping it's disolving ok!

i'm up to about 200 bubbles a minute at the moment for a 55 gallon. Does that seem a bit too high without much success?


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## John N. (Dec 11, 2005)

That's about 3 bps (bubbles per sec). Sounds about right. I have my bubble count set at around 2-4 bps. It really all depends on how well the CO2 dissolves with your diffuser/reactor. If dissolution is poor, then a higher bubble count must be used. Best thing to do is try different methods of CO2 diffusion (powerhead, intake, sponges, glass diffusers, AM 500, inline reactors, etc.) to see which one works best for you, and at a lower bubble count. But 3-4 bps isn't too bad to start.

-John N.


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## geezer (Jun 7, 2006)

Thanks John 

I'm very tempted to try the Eheim intake approach. Do I just use an elastic band or something to tie the tubing to it?

Not 100% sure on how I would attach it


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## geezer (Jun 7, 2006)

I took the bottom off the eheim intake (the little gate thing) and stuck the co2 tube up it.

Hoping that it'll work well now


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