# Gas bubble in reactor



## Noddy65 (Jul 8, 2005)

Hi everyone...sorry if this has already been answered but i couldnt find it anywhere.

Ive made a DIY CO2 reactor using a powerhead and gravel vac (like Tom Barrs one). A gas bubble accumulates very quickly in the top of gravel vac tube.
Is this gas bubble undissolved CO2 or O2?
Does it mean that my powerhead isnt strong enough to create enough turbulance to dissolve the CO2 that im bubbling in?
Im bubbling in around 1 bubble/sec.

I didnt want to drill a burp hole in case this large gas bubble is CO2 as this would just release undissolved CO2 into the atmosphere.

Thanks in advance everyone.

Mike


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## niko (Jan 28, 2004)

There is no clear understanding what exactly is that gas accumulation.

Your only option is to drill a small degassing hole. The wasted CO2 will be very small amount so don't worry about loosing it.

There is no need to use a bigger pump or to reduce the bubble rate - nothing will change. Connecting air tubing to the burping hole and trying to return that gas into the filter outflow hose for example will not work very well. 

--Nikolay


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## Noddy65 (Jul 8, 2005)

Heres an image of what I mean. You can see the large pocket of gas at the top of the tube with the bubbles in the water underneath it.









Mike


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## zeek (Jan 5, 2005)

Check out the Tom Barr venturi design... I think you could drill a small hole near the bottom of that bubble and run a tube from it to the reactor INPUT water flow. The bubble would only get as large as the top of that hole, and according to Tom the reactor does a better job of dissolving the CO2 in the water column. (At least that's what I understand he says.)

I've got the same issue on my AquaMedic 1000. I'm planning on performing the same modification soon.


Isaac


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## lemcc (Dec 19, 2005)

The bubbles and gas pocket are caused by the agitation of the water by the 
Pump the more dissolved gases in water the more gas produced 
The buildup is primarily O2 from photosynthesis
This is a good/free measure of productivity 
More gas = more photosynthesis 
For that reason I don’t vent mine (cheap DO meter)


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## HeyPK (Jan 23, 2004)

You can put a bubble of pure CO2 into the reactor, but, as the CO2 is diffusing out of this bubble, nitrogen and oxygen are diffusing from the water into the bubble. Eventually, at equilibrium, the composition of the bubble will be quite close to that of the atmosphere.


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## Gumby (Aug 1, 2005)

HeyPK said:


> You can put a bubble of pure CO2 into the reactor, but, as the CO2 is diffusing out of this bubble, nitrogen and oxygen are diffusing from the water into the bubble. Eventually, at equilibrium, the composition of the bubble will be quite close to that of the atmosphere.


So if the flow in your reactor is TOO MUCH, is it possible that a pocket of O2/N2 will be created?


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## lemcc (Dec 19, 2005)

if i hook my co2 up to a different diffuser and just run the gravel cleaner and power head 200gph alone during peak photosynthesis it still fills up with gas

the gas can really only be O2 and N2 because co2 diffuses so quickly


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## plantbrain (Jan 23, 2004)

HeyPK said:


> You can put a bubble of pure CO2 into the reactor, but, as the CO2 is diffusing out of this bubble, nitrogen and oxygen are diffusing from the water into the bubble. Eventually, at equilibrium, the composition of the bubble will be quite close to that of the atmosphere.


But that rate is the same very slow rate that occurs with the surface of our tanks, very slow............try dissolving pure N2, or O2 gas in water something, it's extremely tough.

The reverse direction is no different.

How long does it take for a glass of tank water to equilibrate with the air?
Several hours, so it's not instanenous.

You can watch CO2 bubbles disappear as the eminate from a diffuser stone.
Then you can blast them all over the tank also.

You can watch them and see how long they take to dissolve.
Now why would they disappear in the same tank and persist when you blast them around?

Why don't they fill up with gas in both cases?

Regards, 
Tom Barr

Regards, 
Tom Barr


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## plantbrain (Jan 23, 2004)

lemcc said:


> if i hook my co2 up to a different diffuser and just run the gravel cleaner and power head 200gph alone during peak photosynthesis it still fills up with gas
> 
> the gas can really only be O2 and N2 because co2 diffuses so quickly


I directly add CO2 mist to my tanks and watch the mist travel around a tank. 
It does not dissolve immediately.

I can also add the CO2 mist without blasting it around and watch it disappear as the bubbles rise.

How can other dissolved gases degas into the bubble and also have the CO2 gas bubble disappear also?

Note, this is the same tank/same time of day.

Regards, 
Tom Barr


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## lemcc (Dec 19, 2005)

maybe the bubbles actively moving around your tank are bumping into and consolidating with other bubbles making it appear that they presist

like watching one of those bubble ladders co2 bubble gets smaller and smaller then a few small bubbles stick together and float to the top 

my co2 runs 24/7 at night just a few bubbles in cleaner tube 
lights come on and slowly tube fills with gas 
during peak photosynthesis with plants giving off a steady rain of bubbles tube is almost full of gas

co2 levels are highest at night when few bubbles are present
o2 levels are highest when most gas is present
N2 levels which i dont know much about but it would seem that they would remain somewhat constant


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