# Co2 into Filter Intake



## tylerG (Dec 8, 2010)

I've recently set up pressurized CO2 and have decided to "feed" the CO2 into my canister filter intake within the aquarium. Oddly, I hear no noises from the perpeller(sp?) in the filter and do not see any small bubbles coming from the outflow in my tank. 

Could it be possible that the CO2 is dissolving in the canister or is it most likely a "leak" somewhere between the canister and the outflow where the gas is escaping?

Thanks,

-tylerG


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## Seattle_Aquarist (Mar 7, 2008)

Hi tylerG,

Depending upon the model and design of the filter, and the amount of CO2 you are feeding into the filter, it is possible it is all dissolving. Has your PH dropped since you started adding the CO2?


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## tylerG (Dec 8, 2010)

Thanks, Seattle

The canister filter I have is a Rena XP1. 

-tylerG


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## Seattle_Aquarist (Mar 7, 2008)

Hi tylerG,

I have not used that filter in the past. However, if your PH has dropped then the CO2 is being absorbed.


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## niko (Jan 28, 2004)

Tyler,

I have injected CO2 in canister filters before. It works. But it's one of the worst ideas you can come up with as far as aquariums are concerned. Not just planted tanks, any tank.

The biofilter in your canister filter operates in a supressed state anyway. Because there isn't much Oxygen available to the bacteria in a canister filter. The bacteria still cleans your water, but with an efficiency of maybe 50% of what it can do if there was a direct supply of air. A canister filter is convenient, small, and self-contained. But it is not the best place for biofiltration to take place.

By injecting CO2 in the canister you are suppressing the biofilter even more. Now there is not only shortage of Oxygen, but even something else that is worst - the pH of the water is now being made low. The biofilter operates optimally at a pH of around 7.5-8.0. At pH of 7 the efficiency is only about 15%!  And if you inject CO2 in the biofilter itself the efficiency is even less!

So - reconsider the whole thing. It does work but you are basically counteracting yourself. Look for a long post in the DIY about a reactor that you can make for $10. It is just about the most efficient reactor in the market. 

And give your bacteria a break.

--Nikolay


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## tylerG (Dec 8, 2010)

Hats off to the both of you for informative posts!

Seattle - It is beyond me if the CO2 is dissolving. I will definitely check the pH of the tank when I get home. 

niko - 'Glad you took to time to thoroughly explain that process. I have actually used the small reactor you suggested in the past (if it is the small, black filter I'm thinking of). It worked very well but it eventually quit working for some reason. 

I guess I'll explore alternative options to dissolving CO2. Obviously, I'd rather not invest too much money to find a good product. I'd like to find somthing for $30 or under. 'Surely I can find something good for that price. 

Again, thanks a bunch for the info. 

-tylerG


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