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Discussion Starter · #21 ·
I have been using these check valves, https://www.usplastic.com/catalog/item.aspx?itemid=23369&catid=489 in my CO2 system for about 3 years, with no failures yet. I have had, one in my tank, in the water, with CO2 going through it for all of that time, and it still works fine. They are made of plastics that are highly chemical resistant. Shipping costs for buying them drive up the cost substantially, but I still like them. I mistakenly bought the 3/16 inch size the last time, so it can be difficult to slip tubing over them, but they still work. The 1/8 inch size works much better.
cool, order a couple from eBay with free shipping. I think I bought the 1/4" though. I learn a cool trick recently to slip small hoses over an oversized barb. Heat the hose in boiling/hot water. It'll slip right through and when cooled, it's an extremely tight seal.
 

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Discussion Starter · #22 ·
So here it is.



I hooked it up and this is the result


The pressure in the tube determines the water level. I released some pressure by pulling out the air tube and the water level rose into the clear tube part. I also hooked the CO2 line to a DIY yeast generator. Let's see where this goes.
 

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Discussion Starter · #23 ·
Ok, the yeast CO2 is enough to push the water level down.

I've stopped the CO2 coming through by opening the CO2 bottle. I want to see if the water level rises back up as the CO2 dissolves into the water.
 

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One reason the water level might not go back up is that DIY CO2 has a lot of air mixed in, until many days later, and probably always has a significant amount of air. If it is pure CO2 the water level has to rise, since CO2 does dissolve in water very easily.
 

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Discussion Starter · #25 · (Edited)
It looks like you're right. The water level did move up a little as expected when most of the CO2 dissolved in the water, leaving behind most of the other gasses.

I guess I'll have to wait till I get a refill on my CO2 tank.

***
What I can do now is let all of the Non CO2 gasses purge out of the yeast bottle and the reactor chambers. It should be all CO2 by tomorrow.
 

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Discussion Starter · #26 ·
I just read that temperature and pressure influences the rate of gass diffusion into water. The gass chamber is naturally high in pressure so CO2 diffusion should be greater than 1 atmospheric pressure. How much more specifically I don't know. I'd need to find a pressure gauge and a formula to calculate.

Once the chamber is filled with pure CO2, I guess I can time how long it takes for the volume of CO2 to dissolve into water.
 

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Your CO2 diffuser device has its own built-in pressure gauge; just measure the depth of the CO2/water interface in the pipe below the surrounding water. Each inch of water depth displaced is equal to 0.036 psi greater than ambient pressure.

Edit: I'm assuming the device is inside the aquarium, so the aquarium water level is pushing back against the CO2-enriched gas pressure in the tube. If this is all outside the tank, then info above may not apply.
 

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Discussion Starter · #28 ·
yeah, the device is outside the tank, attached to a canister filter.

I like your thinking though. I'll look into it.

Here are some preliminary numbers
Cylinder volume
2" diameter x 7" height
21.99 cubic inch

in 2.5 hours
3.93 cubic inch of CO2 dissolved into the water.
 

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Keep in mind that gases are diffusing BOTH WAYS at the interface: CO2 from your diffuser gas to the aquarium, and N2 and O2 from aquarium to diffuser gas (assuming the diffuser gas is lower in those components). This is similar to how diving beetles and spiders use an air bubble as a "lung" to extract oxygen out of the surrounding water. The change in gas volume is not really a good measure of how much CO2 has dissolved.
 

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Discussion Starter · #30 · (Edited)
yeah, I hadn't thought about the gas exchange coming from the other end.

I'm seeing the a change in rate of pressure as it goes on. I'll post a graph later. I have a drop checker in a 29G tank to make sure CO2 is dissolved in the water. It does go from blue to green.

I was just thinking, this system is impossible to gas/kill your fish. The rate of CO2 is somewhat constant so this is another 'Pro'. Any excess CO2 would leave the chamber and out the tank without dissolving in the water and the rate of dissolving drops over time.
 

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Discussion Starter · #31 ·
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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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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Discussion Starter · #33 ·
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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Discussion Starter · #34 · (Edited)
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
 

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Discussion Starter · #35 · (Edited)
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

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?
 

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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.
 

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Discussion Starter · #38 ·
So according to the formula above,

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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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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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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