# Using Fluval FX5 as CO2 Reactor



## calvert (Apr 29, 2010)

Currently I'm running my CO2 directly into the input line of my Fluval FX5 on my 75g:










It runs through the contents of the canister (foam pads and biomax media) before spitting out thousands of microbubbles. My question is on those microbubbles--is there anything negative about having so many microbubbles in the tank (just cosmetic? inefficient use of co2? etc.) as opposed to being dissolved completely in an efficient reactor?

Some background, I used to use a reactor on the output line of my FX5, but this produced similar results--probably due to the FX5 just moving too much water to serve any purpose powering a reactor--so I took out the reactor on the output line and just fed the co2 into the input line, removing 1 more piece of equipment from the cabinet.

What I'm hoping to get to is it worthwhile to get another small canister or lower flow powerhead to power a Rex Grigg style reactor in order to make that much better use of my co2/getting rid of the microbubbles? This would obviosly mean tossing another input/output line into the tank, which is ultimately what I'm trying to avoid by keeping clutter out of the tank, but will consider it if it's that much better of an option.


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## Eartheater (Aug 13, 2010)

I had a power head on the intake of the FX5 that sent micro bubbles into the FX5 and no bubbles coming out. But that was a bit of an eye sore. If there was a way that you could create smaller bubbles from that CO2 output i doubt that you would see any bubbles.


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## mrchach (Sep 8, 2010)

with alot of water movement like that you may think to make the reactor longer... also adding in some bioballs would help


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## Sharkfood (May 2, 2010)

That particular filter has ultra high water flow. You may wan't to make a 3" diameter reactor. It's gonna push all the air right out of the standard 2" pipe. I have a Fluval 405 on a 2"x36" reactor and there's some blow through. A 3" pipe has a little more than twice the cross sectional area of a 2" pipe, and your filter pushes a little less than twice the volume of water as a 405, so your water speed should be slighly less than what mine is in a 2" reactor. This should be just about right I would think.

The other option is to split your return line and add ball valves to both lines so you can adjust water flow into the reactor until it's optimal for CO2 dissolution with little or no air pocket formation.


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## calvert (Apr 29, 2010)

Sharkfood said:


> That particular filter has ultra high water flow. You may wan't to make a 3" diameter reactor. It's gonna push all the air right out of the standard 2" pipe. I have a Fluval 405 on a 2"x36" reactor and there's some blow through. A 3" pipe has a little more than twice the cross sectional area of a 2" pipe, and your filter pushes a little less than twice the volume of water as a 405, so your water speed should be slighly less than what mine is in a 2" reactor. This should be just about right I would think.
> 
> The other option is to split your return line and add ball valves to both lines so you can adjust water flow into the reactor until it's optimal for CO2 dissolution with little or no air pocket formation.


well, i'm afraid that i don't have the room under the cabinet for a reactor big enough to handle the flow of the fx5, which is why i mentioned adding another option (canister filter, powerhead, etc.) just to power the standard 2"x15" rex grigg reactor.

i'm thinking this is the option i'll most likely have to take--any reccomendations for any particular pumps/powerheads/canisters to do just this? not needed for filtration at all, the only requirements are a small size to fit in my cabinet (i.e. not another fx5) and as little as a footprint as possible in the tank... and obviously, the cheaper the better.

i was looking at just picking up a fluval 105 for this but would like to go cheaper.


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## Sharkfood (May 2, 2010)

I tried running a 2" ID reactor with a 105 and there wasn't enough flow (Big air pocket). 

On the other hand, using the 105 as the reactor by running CO2 into the intake worked fairly well.


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## calvert (Apr 29, 2010)

what flow rate is recommended for a standard 2"x15" rex grigg reactor?


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## topfrog007 (Dec 30, 2007)

Calvert, I may not be much help but here it goes anyways.

I also have an FX5 (tank not set up yet) and have been planning on using cerges reactor.

However if I can just add my Co2 to the input of the FX5 I would much rather do that, if it is effecient. Are your plants doing ok, do you have a drop checker?


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## calvert (Apr 29, 2010)

topfrog007 said:


> Calvert, I may not be much help but here it goes anyways.
> 
> I also have an FX5 (tank not set up yet) and have been planning on using cerges reactor.
> 
> However if I can just add my Co2 to the input of the FX5 I would much rather do that, if it is effecient. Are your plants doing ok, do you have a drop checker?


that reactor looks like a similar setup to one i used to use, before just putting my co2 in my intake line, with the same results... plants are doing good so i'm assuming co2 levels are ok. i did have a drop checker, unfortunately i broke it, so another is on the way. but, i am registering about a full 1.0 point drop in ph from the morning after the co2 has been off all night to later at night when my co2 turns off.

the only thing i'm struggling with right now is dealing with a bunch of co2 microbubbles in the aquarium. i imagine it isn't anything harmful, i'm probably just not using the co2 as efficient as i can be. it looks like i might have to run an external reactor off a separate canister/powerhead, but i'm going to play around with adjusting the flow on the fx5 and/or throwing some filter pads in the fx5 to slow the flow down a bit before i go the separate canister/powerhead route.


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## Sharkfood (May 2, 2010)

Microbubbles are only bad in that they screw up any pictures you try to take. They don't hurt anything.


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## hbosman (Oct 5, 2006)

I'm currently using a cerge reactor powered by an 80 gph water pump and it still spits out bubbles occasionally. It works real well as far as dissolving CO2 but makes a noise like a draining bathtub. I tried it with a 200 gph pump and that just pushed the co2 bubbles straight on through. So I went back to the 80 gph pump. I will try to use different hose materials internally to reduce the noise. Yeah an extra set of in/outs in the aquarium to hide isn't ideal either. If I can get the noise reduced I will continue to use it because it does dissolve CO2 well with the small water pump. If the noise continues, I will go back to misting with a split impeller modded water pump.


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## Jeff5614 (Dec 29, 2005)

The microbubbles don't hurt anything. What matters is if you don't mind the look of them. While misting may not be as efficient as dissolving 100% of the CO2 into the water, it is a very good way of getting CO2 directly to the plant by having the microbubbles adhering to the plant leaves.


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## topfrog007 (Dec 30, 2007)

Will running the CO2 into the intake of the FX5 damage the filters impeller?


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## hbosman (Oct 5, 2006)

Jeff5614 said:


> The microbubbles don't hurt anything. What matters is if you don't mind the look of them. While misting may not be as efficient as dissolving 100% of the CO2 into the water, it is a very good way of getting CO2 directly to the plant by having the microbubbles adhering to the plant leaves.


When I used the misting method, it didn't increase my CO2 usage that much. It's just an esthetic thing. I don't like the noise of either method, bubbles pinging the impeller vs. the slurping sound. When I was using a Boyu inline diffuser, that had a slight bubbling sound. Probably the least intrusive but still mist everywhere. I guess its a personal preference thing when it comes to the type of noise you have to put up with to get away from the mist.


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## blackandyellow (Jul 1, 2009)

The FX-5 has a system to eliminate air inside the canister, I don´t know how injecting the Co2 would affect this system, but it could be expelling the Co2 out of the system because it detects the gas. Doesn´t it make a lot of noise with all the gas inside the system? could it affect the bacteria colonies inside the filter?


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## calvert (Apr 29, 2010)

topfrog007 said:


> Will running the CO2 into the intake of the FX5 damage the filters impeller?





blackandyellow said:


> The FX-5 has a system to eliminate air inside the canister, I don´t know how injecting the Co2 would affect this system, but it could be expelling the Co2 out of the system because it detects the gas. Doesn´t it make a lot of noise with all the gas inside the system? could it affect the bacteria colonies inside the filter?


as far as effecting the bacteria colonies in the filter itself--i don't know the answer to that.

but the fx5's "system" is that where every 24 hours it stops, expels and air built up in the canister, and restarts itself. the only con i read when looking into this was a possible airlock from the build up of co2 inside the canister but with the fx5 this isn't possible.


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## calvert (Apr 29, 2010)

Jeff5614 said:


> The microbubbles don't hurt anything. What matters is if you don't mind the look of them. While misting may not be as efficient as dissolving 100% of the CO2 into the water, it is a very good way of getting CO2 directly to the plant by having the microbubbles adhering to the plant leaves.


thank you. it's hard to find straight answers in this hobby.


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## Sharkfood (May 2, 2010)

Many people run CO2 straight into their canisters, and the bacteria doesn't die.

I have heterotropic sludge in my hoses after the reactor, so apparently they can take the CO2. CO2 isn't displacing oxygen inside the canisters, and bacteria respire through diffusion, not a quaternary protein based transport system like a higher lifeform.

I'm not super familiar with bacteria that are involved in the nitrogen cycle, so I don't know whether they are aerobic only, or facultive aerobes. I know that you would need O2 to make NO3 out of NH3, but like I mentioned, the O2 is still there.


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## hbosman (Oct 5, 2006)

Sharkfood said:


> Many people run CO2 straight into their canisters, and the bacteria doesn't die.
> 
> I have heterotropic sludge in my hoses after the reactor, so apparently they can take the CO2. CO2 isn't displacing oxygen inside the canisters, and bacteria respire through diffusion, not a quaternary protein based transport system like a higher lifeform.
> 
> I'm not super familiar with bacteria that are involved in the nitrogen cycle, so I don't know whether they are aerobic only, or facultive aerobes. I know that you would need O2 to make NO3 out of NH3, but like I mentioned, the O2 is still there.


That's a good point. My output tubes were just as brown as the input tubes to my inline diffuser.


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## calvert (Apr 29, 2010)

fyi.. i did get my replacement drop checker in the other day and put it in this morning. good intense blue going in and has been green/lime green ever since lights on. about 3 bps. i'd say the fx5 definitely does a good job as a reactor.


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## Saverio (Nov 26, 2006)

calvert said:


> Currently I'm running my CO2 directly into the input line of my Fluval FX5 on my 75g:
> 
> 
> 
> ...


Hi, I'm actually considering doing this same thing for my 125. I'm using 2 FX5's, and currently have a ceramic diffuser at each end of the aquarium, but am thinking maybe my CO2 isn't getting spread thru the tank well enough. I was wondering if you are still using yours as a reactor, and if you've still been problem free since you started?


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## calvert (Apr 29, 2010)

Saverio said:


> Hi, I'm actually considering doing this same thing for my 125. I'm using 2 FX5's, and currently have a ceramic diffuser at each end of the aquarium, but am thinking maybe my CO2 isn't getting spread thru the tank well enough. I was wondering if you are still using yours as a reactor, and if you've still been problem free since you started?


yes, and yes.

i'm very satisfied with it. eliminated one more piece of equipment.


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## zackboll (May 27, 2013)

*Interest in using FX-5 as CO2 reactor*

Sorry to bring up such an old post. The original author mentioned using his Fluval FX-5 as a CO2 reactor. I would like to do a similar thing for my 72 gallon planted tank but I am rather new to CO2 injected aquariums.

Do you mind if I ask what plumbing you used to inject CO2 into the intake of your FX-5? Was it compatible with the ribbed hosing of the FX-5, or did you have to get different hosing?

Thanks and sorry for the newbie questions,
Zack


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## shift (Jan 7, 2013)

I would think the "burping" method would expel any built up co2 (partial waste) but would work fine as a reactor when its not burping itself...


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## Wet_Sleeves (Nov 21, 2016)

*FX5 (also FX4 and FX6) method of eliminating air*

The FX line by Hagen Fluval doesn't sense air bubbles inside the cannister... it simply turns off the pump for a few minutes every 12 hours to allow the air inside to work it's way to the top so that when the pumping resumes, the air is flushed out into the tank. You get a few bubbles for a few seconds when this happens.


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