# Don’t all CO2 reactors have limited capacity?



## essabee (Oct 11, 2006)

Can you just go on increasing the CO2 into your reactor and expect all of it to be dissolved? I think not. Once you have achieved the limit any excess will start to accumulate and you would need to burp the reactor. 

Has anyone tried to add an automatic burper/CO2 limiter to their DIY reactors??


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## NE (Dec 10, 2004)

You will reach a limit where the reactor / pump / water will be limiting the co2 dissolving.

I think it is the wrong way to solve the problem, you will not solve more by letting it out.
If the problem is just the accumulated gas lower the co2 injection.
If something is limiting the dissolving of the co2 that should be fixed instead.


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## Rex Grigg (Jan 22, 2004)

essabee said:


> Can you just go on increasing the CO2 into your reactor and expect all of it to be dissolved? I think not. Once you have achieved the limit any excess will start to accumulate and you would need to burp the reactor.
> 
> Has anyone tried to add an automatic burper/CO2 limiter to their DIY reactors??


I can kill the livestock in my tank before my reactors reach a point where the CO2 is building up in the reactor.


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## furballi (Feb 2, 2007)

*Re: Don't all CO2 reactors have limited capacity?*

The amount of dissolved CO2 in a reactor is highly dependent on the exposed surface area between the working fluid and gas, and the mass flow rate of the working fluid.


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## vic46 (Oct 20, 2006)

furballi:
Do you mean flow rate??????????????????????????????????????


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## furballi (Feb 2, 2007)

*Re: Don't all CO2 reactors have limited capacity?*

Mass flow rate of working fluid = flow rate of water across the filter/reactor chamber. Solubility of CO2 is also dependent on temperature and pressure (essentially constant for an aquarium).

An ideal CO2 reactor chamber is a long thin rectangular control volume mounted horizontally on the floor. Position the water's intake and exit ports at each end of this control volume. The CO2 gas "chamber" (air pocket) at the top of the control volume will have a large surface area to mix with the incoming water. The water will move from one end of the control volume to the other end of the control volume.

There is no need to crank up the flow rate of water if there is a large surface area for the CO2 to dissolve into the water. Too much water flow can be stressful to fish.

Let's compare a tall 50 gal hex tank and a 50 gal rectangular tank. The rectangular tank has more exposed surface area. Therefore, it is much more efficient with the exchange of gas into/out of the water.


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## essabee (Oct 11, 2006)

Rex Grigg said:


> I can kill the livestock in my tank before my reactors reach a point where the CO2 is building up in the reactor.


Your reactor design is horizontal; CO2 would not accumulate as the excess would exit with the water flow. Under every condition there has to be a finite amount of CO2 which would dissolve. Your approach is that enough dissolves to be in excess of the requirement of the aquarium, yes I agree that you can always construct a reactor to match your requirement of CO2 for a particular aquarium.

The initial question in my original post is not very good and does not actually get at the point I am trying to make. My apologies to all who read the post, and more so to those who responded.

My rephrased question: - How to determine the size of the reactor (1. Length, 2. Dia., 3. Water-flow.)so that you can get dissolved CO2 required for your aquarium?


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## BryceM (Nov 6, 2005)

CO2 is VERY soluble in water - think of Perrier or soft drinks. The key to an efficient reactor IMO is one that has a relatively slow downward flow with CO2 bubbling upwards in the column. For most applications a 1-1/2" PVC reactor about 18 or 24" long will accomplish this. I use an 18" x 3" dia PVC reactor on my bigger tank that has a closed-loop system driven by a fairly large pump. I agree with Rex though - most reactors are quite capable of killing everything in the tank. The only ones that don't work well are those that are too short or too small - allowing the flow to flush the CO2 bubbles out into the system before they dissolve.


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## Rex Grigg (Jan 22, 2004)

Actually my reactor design is vertical. And excess CO2 would build up in the top of the reactor since that where the water comes into the reactor. Water exits from the bottom.

The size of the reactor is more dependent on the water flow though the reactor than anything else.


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