# canister as a CO2 reactor



## john.shephard26 (Mar 8, 2011)

Hi I have an old Fluval 204 and I want to use it as a CO2 reactor but I've read (can't remember were)that it could damage the canister.What kind of damage could this do?


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## JeffyFunk (Apr 6, 2006)

I believe the concern was that CO2 gas could accumulate in the propeller area, which would cause the motor to overheat. That isn't really a concern these days since the motors used in modern canister filters is magnetic and not subject to overheating like that. Furthermore, this problem can be alleviated simply by utilizing the correct media and CO2 bubble rate (i.e. the canister filter can only dissolve so much CO2 at a time). 

Also, using a canister filter as a reactor will significantly reduce (if not eliminate) any biological filtration capacity of the canister filter since bacteria cannot exist in a high CO2 / low O2 environment. 

I've heard from several PAPAS members that they use a canister filter for dissolving CO2 and have great results. I've tried it myself and didn't find it to be very effective, but that was just my experience.


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## john.shephard26 (Mar 8, 2011)

Actually this is my old canister so it'll be empty, just some sponge for mechanical filtration, so how do you know that its overheating problem and what kind of motors were used before?!I'm just very curious.I thought that it had to do with acidity in the canister forming after dissolving CO2 hm...
Who are "papas members"?


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## JeffyFunk (Apr 6, 2006)

PAPAS = Pittsburgh Area Planted Aquarium Society. I'd have to do some hunting but most Motors are now electromagnetic, meaning that the propeller is turned by an electrical current, not a mechanically moving part. The old types could not be without water for fear that they would overheat. I cannot tell u when they were changed - you'd have to investigate your particular canister filter. I have no idea about the CO2 corrosion issue - I would think it'd be more an issue with cheap flexible tubing, which is always replaceable.


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## john.shephard26 (Mar 8, 2011)

Would you use a canister this way(CO2 reactor)?


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## inkslinger (Jan 1, 2005)

It would cause a Air Lock because the motor sits on top , but a Magnum 350 Canister Filters works good , there motor is at the bottom of the filter work great for my 55g long ago. I remove the media basket and filled with mini bio balls.


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## Bryeman (Aug 24, 2009)

inkslinger said:


> It would cause a Air Lock because the motor sits on top , but a Magnum 350 Canister Filters works good , there motor is at the bottom of the filter work great for my 55g long ago. I remove the media basket and filled with mini bio balls.


This is how I ran my CO2 in my 125g. The Magnum 350's worked great for me for CO2.


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## john.shephard26 (Mar 8, 2011)

I mounted my Fluval yesterday morning, observed all day and I must say I'm not impressed, I can see bubbles going out with the flow and it is obvious this problem with Air lock will cause a lots of headache so I'll bring my cerges reactor back on line.Thank you guys for your input, it was a great help.


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## niko (Jan 28, 2004)

Yes it can be done. I have ran the CO2 through the canister biofilter in at least 5 tanks and it worked. I should say "It looked like it worked". Here's why:

Running CO2 through the biofilter shows gross lack of understanding how the planted tank should be setup as a system of interacting parts. In particular how biofiltration works.

Roughly speaking the kind of microorganisms that develop in the biofilter depends on the supply of Oxygen. If Oxygen is present the filter is aerobic and among other things it "makes" Nitrate. If Oxygen is not present the aerobic organisms step back and anaerobic ones take over. They "eat" Nitrate. Denitrators are built on that simple principle - deprive your filter of Oxygen and your filter that was releasing Nitrate is now a filter full of microorganisms that eat Nitrates as if there is no tomorrow. You can watch a video on Youtube of a guy showing his denitrator reduce 15 ppm of NO3 to 0 (zero) by showing a real time Nitrate testing in a 15 min. long video. Is that a good thing in a planted tank? Are you supposed to have a little Nitrate floating in the water so you "feed" your plants? Decide for yourself (if you understand how the tank is supposed to work as a system).

A successful planted tank with CO2 running through the biofilter demonstrates one other, more important, thing - how the rest of the system can compensate for a big problem with one of the system's parts. Because of lack of understanding we have gone very far abusing this plasticity of the planted tank system. We blast it with too much light, dump dry fertilizers in the water, use questionably nutritious commercial substrates, pump CO2 to sky high levels, neglect the biofilter, etc. But it still works. Seemingly very well: The result is a tank that seems to be running fine but lacks the stability of a proper setup. By stability I mean being able to leave the tank without any care for weeks, even months on end as well as being able to take care of any issues with a predictable outcome. Not very many people even know that such planted tank is possible to establish.


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## john.shephard26 (Mar 8, 2011)

Niko, Niko, You have wasted a lots of space explaining the obvious but thanks for the effort. I'm aware of how the planted tank works(at least the basics), I just wanted to know is it damaging, for the canister, using it as a CO2 reactor.
It did peaked my interest the part about anaerobe bacteria:since I use cerges reactor (its DIY) which basically works on the same principal as an empty canister (water gets in, mix with CO2 and gets out, all in a tight sealed container) can You tell us if the same thing happens there too(anaerobe bacteria eating KNO3)?


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## Octavusprime (Sep 18, 2011)

CO2 solubility has no effect on oxygen solubility in the water column. Thus you can have a high dissolved CO2 concentration AND a high dissolved oxygen concentration. The high concentration of CO2 in your canister may lower your PH in the filter but will in no way create an anaerobic environment in the filter.

I have used my canister as a diffuser in the past. It works but I found it very inefficient. In order to get my CO2 levels to the desired levels I had a lot of gas that just bubbled from the outtake.


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## john.shephard26 (Mar 8, 2011)

Yes, same thing happened here, all though my DIY cerges reactor slows my canister's flow I find it more efficient and no bubbles and very important, after just one day of using my old canister as a reactor, air lock happened only one day after; had to open the canister thinking its all ready busted but beside the magnet being VERY hot my Fluval is working just fine.


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