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Old 07-25-2018, 05:43 PM   #31 (permalink)
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Default Re: Passive CO2 diffuser

Here it is


At 9.5 hour CO2 stopped dissolving into the water. This is perfect for a planted tank. Fill the chamber with CO2 every morning and just let it go for the day.
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Old 07-25-2018, 06:23 PM   #32 (permalink)
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Default Re: Passive CO2 diffuser

A 5 pound bottle of CO2 at 800 psi contains about 3.7 million cubic inches of CO2 gas at 15 psi. Your reactor put about 10 cubic inches of CO2 into the tank in a single photoperiod. So, a 5 pound tank would last about 370,000 photo periods - lets call that 1000 years! (Did I misplace a decimal point somewhere???) I think the problem is that in order to keep 30 ppm of CO2 in a tank of water you have to add many times more cubic inches of CO2 spread out over the photoperiod, because CO2 leaves the water almost as fast as you add it. And, this would mean that your ppm of CO2 in the water is extremely low. I find this hard to believe, so perhaps someone with better decimal point control should do this calculation.
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Old 07-26-2018, 04:46 AM   #33 (permalink)
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Default Re: Passive CO2 diffuser

Lol, no more refilling CO2 tanks!

Yeah, as expected there's a limit to how much CO2 can inject into the tank. If you want more CO2, you'd have add more CO2, maybe 2 x a day instead of once. This is good for low to medium light tanks.

I'll have to fill up the CO2 tank again get this running in a real planted tank.
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Old 07-26-2018, 12:09 PM   #34 (permalink)
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Default Re: Passive CO2 diffuser

Keeping notes
Density of CO2 is 0.0000636574 lbs/cubic inch

or 1762.030766 ppm


***
If you want more CO2, could be as easy as make the vertical chamber longer. It's at 7" now with a 6" clear PVC tube.

***

2,000ppm(air) CO2 becomes toxic to plants

Last edited by mistergreen; 07-27-2018 at 05:40 AM..
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Old 07-27-2018, 05:36 AM   #35 (permalink)
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Default Re: Passive CO2 diffuser

Does anybody know of a formula to calculate 'x' volume of CO2 needed to raise 'x' volume of water to a certain ppm of CO2?

never mind, found it

Quote:
Width x length x height x desired CO2 level in parts per million.
For example, if you have a 8x8x7 foot grow room, you would need to cover 448 cubic feet ( 8x8x7=448 ). To compute the amount of CO2 required to raise the level to 1,000ppm use this equation.
Width x length x height x desired CO2 level in parts per million.
So in our example, we have 8x8x7x0.001 = 0.448 cubic feet of CO2 needed to raise the level inside the grow room to 1,000ppm CO2.

Keep in mind this is ppm by volume (in air)... PPM in water is by weight. There's another formula to convert that.... It's easier to convert everthing to volume for the above formula.

16,500 ppmv = 30 ppmw

yikes, we're pumping a lot of CO2 into the tank. Anybody have health issues from this?

Last edited by mistergreen; 07-27-2018 at 06:06 AM..
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Old 07-27-2018, 05:52 AM   #36 (permalink)
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Default Re: Passive CO2 diffuser

Quote:
Originally Posted by hoppycalif View Post
A 5 pound bottle of CO2 at 800 psi contains about 3.7 million cubic inches of CO2 gas at 15 psi.
From what I'm reading
Quote:
A pound of liquid CO2 in a tank contains 8.741 cubic feet of gas
So a 5 pound is 75522.24 cubic inch of CO2, not 3.7 mil
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Old 07-27-2018, 06:39 PM   #37 (permalink)
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Default Re: Passive CO2 diffuser

Quote:
Originally Posted by mistergreen View Post
From what I'm reading

So a 5 pound is 75522.24 cubic inch of CO2, not 3.7 mil
That is the volume of CO2 at about 700 psi. Multiply it by 700/15 to get the volume at 15 psi. (It is still 5 pounds of CO2).

EDIT:
I'm wrong! Wikipedia says CO2 density at one atmosphere and about 70F temperature is 1.98 kilograms per cubic meter. That means 5 pounds of CO2 at one atmosphere (15 psi) and 70F is about 70,000 cubic inches. This time I used the back of a piece of scrap paper instead of an envelope, so it is more accurate.

Last edited by hoppycalif; 07-28-2018 at 05:53 AM.. Reason: Fix mistake
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Old 07-28-2018, 05:20 AM   #38 (permalink)
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Default Re: Passive CO2 diffuser

So according to the formula above,

Quote:
Width x length x height x desired CO2 level in parts per million.
To raise a 29G tank to 30ppm
12"x18"x30"x0.0165

I need 106.92 cubic inch of CO2.
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Old 07-28-2018, 10:01 AM   #39 (permalink)
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Default Re: Passive CO2 diffuser

Quote:
Originally Posted by mistergreen View Post
So according to the formula above, To raise a 29G tank to 30ppm
12"x18"x30"x0.0165 I need 106.92 cubic inch of CO2.
True, for complete CO2 dissolution in a sealed tank with no other CO2 inputs or losses. But that's just a snapshot quantity, not a rate of CO2 input. Now let's estimate the CO2 loss into the air, plant uptake, CO2 production by animals and bacteria ... might need research grade lab paper towels for those calculations ... have at it!
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Old 07-28-2018, 12:20 PM   #40 (permalink)
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Default Re: Passive CO2 diffuser

Quote:
Originally Posted by Gerald View Post
True, for complete CO2 dissolution in a sealed tank with no other CO2 inputs or losses. But that's just a snapshot quantity, not a rate of CO2 input. Now let's estimate the CO2 loss into the air, plant uptake, CO2 production by animals and bacteria ... might need research grade lab paper towels for those calculations ... have at it!
I checked my desk - no paper towels of any kind. Sorry.

Actually we have enough information to come up with a crude answer, but my mind isn't in it yet.
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