# Injecting co2 into canister filter



## Whisner (Jun 23, 2011)

I am about ready to put co2 into my 70 gal. with eheim 2073 canister filter, inline heater, ultraviolet sterilizer, Milwaukee regulator and controller. My question is if I inject co2 into the canister filter do I need a reactor or diffuser? 
Thanks for the help.


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## WaveSurfer (Oct 3, 2007)

Whisner said:


> I am about ready to put co2 into my 70 gal. with eheim 2073 canister filter, inline heater, ultraviolet sterilizer, Milwaukee regulator and controller. My question is if I inject co2 into the canister filter do I need a reactor or diffuser?
> Thanks for the help.


There are many possible methods but for me, I chose direct injection of CO2 under the filter inlet for simplicity.

I actually made use of a part from an unused hang-on filter to aid capturing of the CO2 bubbles from the tube and diverting them into the filter inlet:


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## Whisner (Jun 23, 2011)

Can I put a tee in the inlet tubing of the canister filter, reduce it down to a barb fitting and connect the co2 tubing to the barb on the tee?
Thanks


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## kris66 (Jan 3, 2011)

i read somewhere that CO2 can kill off your BBB if you put the tubing into your filter inlet. Is that true at all?


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## Jeff5614 (Dec 29, 2005)

kris66 said:


> i read somewhere that CO2 can kill off your BBB if you put the tubing into your filter inlet. Is that true at all?


I've read quite a bit on that also including remarks by ADA that too much CO2 and lack of oxygenation will harm the biofilter. From what I've read, the activity of the bacteria is greatly diminished at a pH of less than 6.5 and pretty much grinds to a halt below 6.0. I have injected CO2 into a canister in the past and it worked really well but I'd not do it now based on what I just mentioned. Here's a link that addresses and that and a few other related items.

http://www.oscarfish.com/article-home/water/71-autotrophic-bacteria-manifesto.html


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## Sharkfood (May 2, 2010)

Injecting CO2 into a canister inlet definitely works. I initially was injecting that way, but stopped when I purchased a larger filter because the CO2 bubbles were making a loud tapping noise inside the tubing.


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## WaveSurfer (Oct 3, 2007)

Just sharing:

I just removed the inlet netting few moments ago and decided to just plug the CO2 tube directly into it. Reason was that CO2 bubbles were leaking out when I tried to increase the CO2 input using my previous method (see my above post).


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## oscarsx (Mar 15, 2011)

Won't putting the co2 directly under the intake of the filter cause problems with the propeller?

never tried it before, but If not, this sounds like a good idea.


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## ADA (Dec 31, 2010)

Regarding the theory that Co2 will reduce the good bacteria in a canister filter, it doesn't make sense to me. Regardless of where you add the Co2 (to the tank, to the filter, through a diffuser, etc, it's going to get into the canister at some point. The drop in PH from using Co2 will cover the entire tank AND canister. So, whether the co2 is getting sucked directly into the canister, or dissolved in the aquarium THEN sucked into the canister, what difference does it make?


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## fresh.salty (Jul 2, 2010)

The pH may be lower in the canister filter if injected directly since it's less diluted.


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## ADA (Dec 31, 2010)

fresh.salty said:


> The pH may be lower in the canister filter if injected directly since it's less diluted.


Low enough to make a difference? Remember the water is constantly flowing through the canister. The Co2 doesn't get pumped in there and just sit there. The cycle is very fast.. so you have fresh new water from the tank in your canister every minute or so.


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## fresh.salty (Jul 2, 2010)

IDK, that's why I say "may be". 

Regardless, I couldn't do it that way without air building up in the canister. My bubble rate is way beyond the countable range, almost a stream.


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## sayurasem (Jun 17, 2011)

I don't think its a good idea, just for the sake of the impeller.


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## fresh.salty (Jul 2, 2010)

10 bubbles of CO2 will have a much greater impact on 1 gallon in the canister than it will on 40 gallons in the tank, a random example.


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## ADA (Dec 31, 2010)

fresh.salty said:


> 10 bubbles of CO2 will have a much greater impact on 1 gallon in the canister than it will on 40 gallons in the tank, a random example.


Yeah, I'm not trying to argue with you..  This is what I'm talking about though.. I don't think you can think of the canister as a "1 gallon" container. My point is, the water is constantly moving through it, way too fast for it to make any difference. If you pump 10bps into a 1 gallon tank, sure the co2 content in the water will be much higher than a 40 gallon. But that's like saying that one corner of your 40 gallon tank is an independent 10 gallon body of water.

So the canister is just an extension of the main tank.. just like a sump. I reckon if you turn everything off at any time, and test the water in the filter (providing you don't shake it up) and the water in the tank, you're going to get the exact same PH reading, as well as every other reading.


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## ADA (Dec 31, 2010)

In fact, a lot of people that run sumps don't even bother taking water samples from the main tank because the sump is more accessible. They just scoop it out of the sump.


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## sidefunk (Apr 22, 2010)

I had my boyu inline diffuser running on the intake for some time a while back and the air trapped in the filter drove me crazy. For this reason alone I would not want to run co2 into the filter again, but if your filter doesn't seem to trap air then it seems to be an effective method of diffusion which others have had success with.


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## tr182md (Dec 5, 2011)

*Inline diffuser*

I think an inline diffuser seems more elegant. This one is impressive and is on outflow so no problem with air trapping noise. Might try this next. 

http://greenleafaquariums.com/co2-diffusers/atomic-inline-diffuser-16.html


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## ADA (Dec 31, 2010)

sidefunk said:


> I had my boyu inline diffuser running on the intake for some time a while back and the air trapped in the filter drove me crazy. For this reason alone I would not want to run co2 into the filter again, but if your filter doesn't seem to trap air then it seems to be an effective method of diffusion which others have had success with.


Yeah that's a good point. I have heard of that happening. Mine has been running a few days now, and every now and then a pocket of air is spat out. Filter seems fine. Inline on the outflow does seem better. The only thing I would wonder, is do you get as much dissolving this way? Going to the intake seems like it would disdolve better. Do you have to diffuse the co2 on the outflow? I wonder if you could just install a co2 line directly in to the outflow.


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## ADA (Dec 31, 2010)

tr182md said:


> I think an inline diffuser seems more elegant. This one is impressive and is on outflow so no problem with air trapping noise. Might try this next.
> 
> http://greenleafaquariums.com/co2-diffusers/atomic-inline-diffuser-16.html


True. I love GLA stuff


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## rroginela (Sep 24, 2011)

*Doing this on my XP1*

Hi,

I'm doing in-line injection into the intake right now... I drilled a hole right into the inlet tube above my basket and stuck the tube right in there... Great dissolving power! I almost gassed my fish because it was so much more efficient then the previous method I was using... No problem with noise at about 2 bps (subjective measurement). Of course all of this depends on a great deal of factors so trial and error is the best way to go... you can always patch a hole in your intake (epoxy is the god of glues  ) if you are unhappy with it and go another way...

Rafal


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## ADA (Dec 31, 2010)

rroginela said:


> Hi,
> 
> I'm doing in-line injection into the intake right now... I drilled a hole right into the inlet tube above my basket and stuck the tube right in there... Great dissolving power! I almost gassed my fish because it was so much more efficient then the previous method I was using... No problem with noise at about 2 bps (subjective measurement). Of course all of this depends on a great deal of factors so trial and error is the best way to go... you can always patch a hole in your intake (epoxy is the god of glues  ) if you are unhappy with it and go another way...
> 
> Rafal


Awesome! So, no diffuser at all.. ? What size is your tank?


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## Daximus (Oct 19, 2011)

Cool ideas! That inline reactor linked above is sweet too. 

I'll be running an airstone a few inches under my can's intake. I figure the small bubbles are sucked up, then they will try to rise as the water is going down into the can...hopefully that process diffuses some of them. The others will probably wander around my can for a bit, lol. 

This will be my first try at this setup today...I'll let you know how it works.


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## rroginela (Sep 24, 2011)

ADA said:


> Awesome! So, no diffuser at all.. ? What size is your tank?


75g

Rafal


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## HD Blazingwolf (May 12, 2011)

its not the level of c02 that will kill bb. its the possibility of bubbles or pools of c02 build up against the media and oxygen is not making it to that section. it can kill small sections or large setions.. the key to preventing this is good flow. it has nothing to do with ph in the cannister. just the possibility of oxygen deprivation in certain areas.

clean filter media with good flow will prevent this in most cases

the bubbles will slowly degrade your impeller. if you don't mind replacing the impeller and keep ur media free flowing. it won't be a problem at all


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## RSidetrack (Jul 17, 2011)

Just a couple thoughts from my experiences:

It seems the Rena Filstar's have some issues when running the CO2 into the inlet - sometimes the gasses build up on the intake valve the the siphon stops, or air builds up in the filter and reduces efficiency. I stopped putting it through my filstar because I would come down some mornings and the filter was chugging and not pushing water through. As a result I placed the line into the inlet on a power head - works great.

As far as the milwaukee regulator - be very careful. I just lost several fish because the solenoid did not cut off and gassed my fish - and the flow is very hard to control - especially when the tank starts going below the initial pressure.

As for the BBB getting hurt by the CO2, it all depends on the amount you are injecting. If you put a ton of CO2 in (tons of bubbles per second) then the concentration in the filter will be higher than once it mixes in with the rest of the water. The important thing is to make sure that there are good O2 levels in the water as the BBB need the O2 to survive. It should not impact them if you are doing flows of 1-10 bbs, but if you go extreme it could impact the BBB, but otherwise it should be very close to the rest of your water levels. This is just a theory - I am not a scientist by any means and I could be completely wrong - so take this with a grain of salt.

Also - I am not sure which filter you have, but if it is a Rena, they have a valve attachment that allows you to control flow. On the inside of the knob there is a piece you can pull off and is made for an air line. This is on the outlet side and will break the bubbles up - though not highly efficient, it would be the safest place IMO.

Good luck to you! And remember, the milwaukee regulators/solenoids/valves can be a problem, here is my thread with the issue in case you feel like doing some reading: http://www.plantedtank.net/forums/general-planted-tank-discussion/157014-very-sad-day-today.html


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## Elrodg (Sep 14, 2011)

Why not just attach to the outlet hose and directly flow into the tank? If you are already using a diffuser, why diffuse further?


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