# CO2 Diffusion



## Aeropars (24 Apr 2008)

Firstly, here's my hardware:

The CO2 reactor:






The filter: 





It appears that I could be wasting a lot of CO2 using my current configuration as I'm getting gas spurts coming out the filter outlet. The reactor is advertised as being suitable up to 1000 liters and I'm using it on a 180 liter so i would expect it to be highly efficient for this amount. The filter is capable of about 1400 lph which is about whats recommended on this filter.

Having met Dan this week and saw how little CO2 he gets through, its opened my eyes that I'm not running efficiently.

My current 2kg bottle of CO2 has lasted for about a month while Dan can stretch his for 4 months while maintaining 30ppm. He is using a ceramic reactor into his external filter.

My current configuration is as follows:

Filter inlet > Filter input > Filter output > CO2 Reactor > Filter Outlet

Any ideas on how I can get better diffusion?


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## milla (24 Apr 2008)

I have this reactor on a 180L tank using 600g bottles which last 4-6 weeks (on 8hrs a day) @ approx 3bubbles per sec.
I never see gas spurts. Filter is 1200lph
Probably a daft question but you have got the water flow going the correct way through the reactor ?
The water comes in at the top on this reactor with the gas coming in at the bottom against the water flow.


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## Aeropars (24 Apr 2008)

I beleive so, input at the top, output at the bottom so the gas has to fight against the current as it rises.

Incidentally, is your reactor perfectly verticle? Mine is about 2mm off but wondered if this could be the cause.


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## beeky (24 Apr 2008)

I don't understand why you'd be getting gas spurts unless the gas is going into the inlet of the filter, but from what you said you have the gas being added on the way out.

Interesting point about the water flow. I've got a reactor that's very similar and about to be plumbed in, so very good timing!


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## Aeropars (24 Apr 2008)

I would have said gas suprts would be less likely if the co2 reactor was on the filter input site as any gas escaping would have more time and turbulence to disolve in the water. Thats what some people do with their ceramic reactors deliberatly putting them beneath the filter inlet.


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## LondonDragon (24 Apr 2008)

I was also thinking of getting one of those reactors, are they really better than a ceramic diffusor inside the tank?
thanks


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## Dan Crawford (25 Apr 2008)

Could these spurts or burps be just a build up of oxygen and other gasses which in a situation without the reactor in the line of flow would just be expelled into the aquarium without a noticeable burp? A lot of people who have their diffuser placed just below the filter inlet see this happening (in this case it's a build up of CO2 within the external)
Just a thought.


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## Aeropars (25 Apr 2008)

I dont think so as I've turned the CO2 down a little and it stops it although I'm not sure how much effect this will have on the amount of CO2 in the water.


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## Aeropars (27 Apr 2008)

Well, I turned the CO2 down a little and i'm still getting spurts coming out of the filter outlet. Really frustrating as i'm certain i'm wasting a lot of CO2 with it. Anyone got any further suggestions?


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## Aeropars (28 Apr 2008)

Not wanting to sound like a moaning Grandad but it would be benificial to create your own thread. It stops threads getting hijacked and dtreacting from the original subject.

I've split the thread to avoid any problems.  Ed.

Back to my problem, I noticed yesterday that there was a buildup of co2 right at the bottom of the filter which i pre4sume is stopping the co2 from rising against the current to the top of the reactor. Does anyone know how to clean these things?


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## milla (28 Apr 2008)

Is fairly easy to clean.  The top unscrews so you can remove the green net and rinse through.


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## Aeropars (28 Apr 2008)

See, I never knew that! James just let the cat out the bay on a PM i sent him 

I'll have to give that a go then!


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## Aeropars (13 May 2008)

Well I happened to get my 500gram JBL bottle on the go about 2 weeks ago and today it ran out. 

I really do think there is something wrong with the diffusion happening in the reactor as I would expect the  CO2 to last at least a month on a 500 gram. 

I'm still getting loads of constant little bubbles coming out the filter outlet which i'm pretty sure is CO2 being wasted. 

Do you think by adding more mesh to the reactor that this will help?


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## Aeropars (15 May 2008)

I had a reply from the company who sold it to me and he said i need to reduce the flow! Highly miffed at this response as this is advertised as suitable for 1000l tanks! You would need even more power filtration on a tank that size so would cause this problem even worse!!

Any thoughts guys?


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## milla (15 May 2008)

I was under the impression that the 1000L refered to a flow through rate of upto 1000L/ph not the size of tank.


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## ulster exile (15 May 2008)

Ditto, its suitability refers to the filter's flow rate.  I would have thought that if the CO2 is effectively being 'stuck' at the bottom near the inttake, this is an indication that the water flowing from the top is too powerful to let the reaktor do its job.


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## Aeropars (15 May 2008)

Well, I cant see the gas being stuck at the bottom although it is difficult to see.

I'm half tempted to reverse the  inlet and outlet so that the bubbles get churned up in the filter as well.


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## JamesC (16 May 2008)

The reactor is for a 1000 litre tank. I would be amazed if your filter is too powerful as I have a more powerful one and I'd say it was really only just powerful enough to work the reactor (Eheim 2028 btw). CO2 dissolves so quickly it is unlikely that these bubbles are CO2, but more likely oxygen or nitrogen. If your filter isn't providing enough flow through the reactor you tend to get a gas buildup at the top which casuses a lot of splashing and more gas (O2?) to come out of solution. The splashing causes small bubbles that come out of the bottom of the reactor and into the tank.

Having a gas buildup does decrease the efficiency of the reactor but not to a great extent IMHO. I have a 200 litre tank and it goes through 6.35kg of CO2 in 6 months which equates to about 500g every two weeks.

Before I had the Eheim I used a Rena XP2 which I replaced as it wasn't up to the job. I used to get the daily build up of gas at the top of the reactor and small bubbles coming into the tank and also used to think that perhaps it was CO2. What I did to test if it was or not, was to pump in loads more CO2 very quickly into the reactor to add a couple of inches to the height of the gas buildup. Then turn the CO2 off and watch what happened. What I saw was that within several seconds the gas level went straight back to where it was before adding the extra CO2 demonstrating to me that CO2 was still being readily dissolved and that the remaining gas most likely wasn't CO2.

James


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## a1Matt (16 May 2008)

You could easily add a venturi loop to your existing reactor. This would then reduce any gas build ups as they occur (be they spurious gases or C02), allowing your reactor to run at full efficiency (however good that may be! )

The venturi is Tom Barr's design and he has details on his website for both internal and external versions:

Internal:
http://www.barrreport.com/estimative-in ... esign.html
External:
http://www.barrreport.com/articles/3444 ... actor.html

I DIY'ed an internal one (out of an old gravel cleaner and spare tubing I had and a Â£5 pump off ebay) and it works well. (FWIW at apprx 0.5-.75bps my 2kg bottle lasts 6 months or so.)

It took me 15 minute to make and hell of a lot longer to fully undertand how it works!


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## Aeropars (16 May 2008)

Whats Venturi?!


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## Steve Smith (16 May 2008)

Venturi is a water current, like a whirlpool.


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## a1Matt (16 May 2008)

Aeropars said:
			
		

> Whats Venturi?!



In practical terms relating to the CO2 reactor, you take a length of airline tubing and insert one end in the reactor and the other end of the tubing you place anywhere in the water flow just before the input to the reactor. This creates the venturi loop which removes any pocket of gas in the reactor.

My understanding of the science is not good enough for me to be able to decontruct it concisely for you.  A bona fide explanation of the science can be found here, but you might find it a bit esoteric....  http://en.wikipedia.org/wiki/Venturi_effect" onclick="window.open(this.href);return false;"

To expand in the comment in my last post about whether this would be of any use to you; if you were to notice a large pocket of gas at the top of the reactor and one end of the venturi loop was terminating inside this gas bubble it would effectively remove the gas bubble.  The gas has to physically enter the venturi loop to be removed though, so if you can not actually see any build up of gas in your reactor then the venturi loop won't help you.

It sounds like you have a gas build up somewhere though, or you wouldn't get the spurts out of the filter outlet. To my mind the logical place is the reactor, but you might have other factors that are having more of an influence that I haven't thought of.

If you want to get your head around the venturi concept further I recommend you to do what I did which is to spend a few hours poring over the links to the venturi I posted before.  There is a picture of the internal reactor that clearly shows the extra tubing for the loop and the placement of it.


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## ceg4048 (16 May 2008)

Hi,
    A venturi is based on two simple principles:
The first is that as the velocity of any fluid (gases included) increases, it's pressure necessarily decreases.
The second principle is that as a fluid approaches a restriction it's velocity must increase to avoid a vacuum near this restriction. 

The hourglass shape of the venturi comes in handy therefore because as the fluid approaches the "throat" it speeds up through this restriction and the pressure is at its lowest because of this increased velocity. As the restriction eases on the far side of the restriction the fluid flow slows down and it's pressure rises. 

This is how a some clever guy invented the carburetor. Fuel is injected at the "throat" of the venturi section of the carburetor and dissolves in the air stream. The low pressure at the throat "sucks" the fuel out into the engine. As you open the throttle the airflow rate increases and the pressure drops even further dumping more fuel into the airflow so the engine accelerates.

This venturi phenomenon also works on an airplane/bird wing as the wing is larger on top than it is on the bottom. As a result the airflow on top of the wing accelerates more than it does on the lower surface lowering the pressure on the top side. Because the pressure is higher on the lower surface than on the upper surface this pressure difference causes an upward force we call "lift".

Cheers,


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## Aeropars (17 May 2008)

Clive... you blow me away with nearly all of your posts!

Can someone get that man a glass of wine??


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## a1Matt (17 May 2008)

Aeropars said:
			
		

> Clive... you blow me away with nearly all of your posts!
> 
> Can someone get that man a glass of wine??



I second that


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## ceg4048 (18 May 2008)

Make that a Pinot Grigio please....  

Cheers,


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## Arana (18 May 2008)

ceg4048 said:
			
		

> Make that a Pinot Grigio please....
> 
> Cheers,



I had you down as a Pomerol man


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## ceg4048 (18 May 2008)

Arana said:
			
		

> ceg4048 said:
> 
> 
> 
> ...



Love all the Merlots - Pomerol, Graves, St. Estephe, Lusac - but they are too expensive, just like some ferts I know.   Better value can be found with the Spanish reds Tempranillo or Ribera del Duero (Riojas suffers from "me too" Gucci syndrome ).  

Cheers,


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