# CO2 diffusion in a large tank



## Gumby (Aug 1, 2005)

Kind of a fert question:

I have a 125gallon tank with a sump on it. The return pump does 1280gph. I have previously tried putting the CO2 line into the intake of the return pump to diffuse the CO2. 

This doesn't seem to work as well as I had hoped. 

I was thinking about buying a seperate canister filter to diffuse the CO2. Do you think this would work? If so, which canister filter works best as a diffuser? If not, what's the best method of diffusing CO2 in a large tank?


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## Laith (Sep 4, 2004)

I would think that for that size of a tank, the best solution would be a CO2 reactor rigged to the output of a cannister or the return of your sump.

The basic design can be seen in the Aqua Medic 1000 CO2 Reactor. Many people make their own. Do a search on DIY CO2 reactors.

The sump itself may also be a source of CO2 loss unless it is closed and not open...


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## Phil Edwards (Jan 22, 2004)

Gumby,

I used to use a sump on my old 90g and had success putting the CO2 output directly into the return pump's intake. It required more gas than I thought it would to maintain sufficient levels, but it worked. When I moved I made a new one out of a 20L and had a glass cover made to fit it completely. After putting duct tape along the edges to seal it off it worked a lot more efficiently. I had also added an external DIY style reactor to the return line for even more increased efficiency.

If you desire to go the canister filter diffusion route don't bother with getting a reactor, just put the CO2 line next to the filter intake and use the filter itself as the reactor. Cable/Zip Ties are great for holding gas lines against the intake tube. If you go this route I would suggest getting a small foam filter block such as one used for an AquaClear Mini/20? and put that over the intake to reduce the amount of particulate matter that gets into the filter. Fill the canister chamber with ceramic bio-media or small bits of pumice to increase the turbulance within the canister and there you go, a nice CO2 reactor.

If you want to go all-out, this is the way to go-
http://www.aquabuys.com/miva/mercha...2_set_dlx_05&Category_Code=i2&Product_Count=1

Regards,
Phil


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## plantbrain (Jan 23, 2004)

I'd seriously reduce the flow rate off the pump, you 'll only need about 1/2 that flow rate.

I'd make a 18"x 2 or 3" dia PVC tube and fill with biomballs and cap each end and run water in the top and CO2 rich water out the bottom.

Should cost no more than 10$ and feed the outflow right into the return pump's suction side.

Reduce the overflow splash to about 4" below the tank's surface level, tape up any air holes on the wet/dry tower.

I'd feed the CO2 directly into the pump's suction side that drives the CO2 reactor. 300-400gph will be fine and a rate of about 2 bubs a sec to start and then increase as needed.

Regards, 
Tom Barr


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