Use Canister filter for CO2 reactor


Junior Poster
Jun 30, 2007
Got half of my kit through today and now have the hardscape set up :)

The CO2 diffuser that came with my CO2 kit though is big and ugly. I have seen a few people mneiton that they have their CO2 running into the intake pipe of their filter which then acts as a big reactor.

How well does this work? I would imagine that the water would be much more enriched but you would problably need to use more CO2? Also I'm guessing that putting CO2 through the filter is going to screw up the biological filtration a bit?

Does it work or would I be better off building myself an external reactor? I'm using a Fluval 305 filter.


Junior Poster
Apr 18, 2007
Hi Barney.i run an Eheim classic filter in my 160 liter tank with the co2 line,inline on the intake side of the filter. Has been about 4 months now,and i think it works very well.Seems to desolve the co2 quite well.The only adjustment i had to make was to make the output pipe from the filter, the same depth as the intake pipe in the inside of the tank.Seems to desolve the co2 better,and theres no surface movement.Hope this helps and makes sence.


Prolific Poster
Jan 28, 2007
I have an Eheim Pro II on my main tank and when I first started dosing CO2 I connected the CO2 supply to the suction side of my filter. It seemed to work pretty well as far as getting CO2 into solution but I ended up making a nice external reactor that operates on the discharge side of the filter because of frequent and very annoying purging of built up gasses in the canister.