# CO2 reactor question



## Tomoko Schum (Apr 7, 2005)

Hi y'all,

I am thinking about making a DIY external CO2 reactor for my 75G tank. Can I use a DIY external reactor on the output side of an Eheim 2026 Pro II canister filter? Does an external CO2 reactor reduce the return flow from the Eheim filter too much? 

What's the current thought on using a canister filter as a reactor? Some people objected doing this in the past saying that CO2 will kill off the filter bacterial in the reactor.

TIA,

Tomoko


----------



## Spyke1969 (Dec 3, 2004)

Using the canister as the reactor can possibly cavitate the pump causing problems & stress on the impeller. I built an external reactor for my xp2 and didnt see any real loss of flow. I did see a noticable growth in my plants over the internal powerhead spraying it into the tank. I am not sure about killing the bacteria in the filter.


----------



## lenosquid (Oct 9, 2006)

I built an external co2 reactor (like gomers) and had it on the output side of the 2126 filter and it works great. I have a 55 gallon tank and the flow has been just fine.


----------



## jeff5614 (Feb 15, 2006)

Same experience here. I've gone to an external reactor with no apparent change in flow.


----------



## Leonard (Mar 4, 2007)

I don't think the bacterias will be hurted by the CO2 (acid). I will remeber that we disscused this some time ago (not on APC), and we supposed it wouldn't hurt them, otherwise, they should seem to like it better (than ordinary aquarium-water).

Exuse my bad english :S


----------



## freydo (Jan 7, 2006)

the problem with have the co2 going straight into your canister filter is that co2 gas will build up in the creating quite a bit of noise. and as Spyke1969 mentioned, it will put some strain on the impeller.

as everyone here has mentioned, i'm also running my diy co2 reactor on the outflow of my XP3, without any noticeable restrictions to the flow.


----------



## Tomoko Schum (Apr 7, 2005)

Thank you for all the input.
I noticed that Gomer's plan for the external reactor has 3/4 inch hose barbs. My Eheim 2026 has 1/2 inch ID pipes. I suppose I can use 1/2" hose barb instead of 3/4 inch one without any problem. Have any of you done this?

Tomoko


----------



## Leonard (Mar 4, 2007)

I was wrong!
The filterbacterias gets hurted by a low pH! But the plants are compete about absorb nutrients (that filterbacterias would have done if you wouldn't have plants), so you don't really need them so much.
Even if don't diffuse the CO2 in your filter, you anyway gets a lower pH in the water, so I don't know if it really matters.


----------



## Left C (Jun 14, 2005)

Tomoko Schum said:


> ...My Eheim 2026 has 1/2 inch ID pipes...


I just want to save you a little trouble. The 2026 doesn't use 1/2" ID tubing.

The Eheim 2026 uses 16/22mm tubing. This works out to 5/8" ID by 7/8" OD.

Metric Tubing Conversion 
9/12mm = 3/8" 
12/16mm = 1/2" 
16/22mm = 5/8" 
25/34mm = 1"

http://www.drsfostersmith.com/produ...&Ntx=mode+matchallpartial&Np=1&pc=1&N=0&Nty=1


----------



## vic46 (Oct 20, 2006)

http://www.aquaticplantcentral.com/forumapc/attachment.php?attachmentid=471&d=1099597504

Great diffuser designed by Gomer on this board.

Vic


----------



## Rex Grigg (Jan 22, 2004)

I show the 2026 has having 5/8" input and 1/2" output lines.


----------



## Left C (Jun 14, 2005)

That's not right. I have the 2028.

The 2026 and 2028 use the same 4005940 tubing on both the intake and the exhaust which is the 16/22mm tubing. It's shown on page 1 of this link.
http://www.eheim.de/eheim/pdf/en/ersatzteile/afilter/2026-2128_prof_II_GB.pdf

Sometimes, it's simply referred to as the 594 tubing: http://www.thatpetplace.com/pet/product/productInfo.web?infoParam.mode=1&infoParam.itemKey=211295


----------



## fishtastico (Feb 28, 2007)

Tomoko Schum said:


> Thank you for all the input.
> I noticed that Gomer's plan for the external reactor has 3/4 inch hose barbs. My Eheim 2026 has 1/2 inch ID pipes. I suppose I can use 1/2" hose barb instead of 3/4 inch one without any problem. Have any of you done this?
> 
> Tomoko


I built one to work with the 1/2" hose from my eheim. The tube you see in the foreground is the 1/8" barb with the C02 tubing coming in. On the bottom is the water input, run from the output on the eheim.

Photo of C02 reactor

I followed one of the instructions online... did not use bio balls in my reactor. I ended up picking up some extra 1/2" hose because the hose pieces I had were not the right sizes - but so far it's working fabulously.

My output is on the sprayer bar, set vertically rather than horizontally.

I recommend ordering the small parts online from some place like McMaster, because it took several trips to 3 different home improvement stores to find the small connecting bits but it all worked out in the end. Swap out 3/4" connectors for the 1/2" connectors to fit your eheim and you're good to go.

Here's a photo of one corner of the tank taken from my camera phone. (this tank has been up for about 3 weeks now.. getting ready to start on the ferts).










The tank is doing very well so far - hopefully it will continue to do so.


----------

