CO2 Diffuser under Fluval 207 Canister Filter

I have my CO2 diffuser directly under my Fluval 207 Canister Filter intake and all the bubbles can be seen going into the intake. My drop checker does not really go as green anymore, as it was before when I used the flow of water to disperse the bubbles.

Also, something I've noticed is that after the diffuser turns off, the canister can be heard to make loud "burps", which is normal for this setup but I notice it's only happening after the diffuser stops letting bubbles out into the intake.

I'm wondering if I'm missing something here, as people online said diffuser under intake is a good idea, I'm not seeing better results. I've thought to use an in-line diffuser but I'm not sure how to go about with the ribbed hose the Fluval canister provides.

 

The defuser should be on the outlet side so the flow disperses the bubbles around the tank
Bubbles going into the filter have to escape somewhere so what you are hearing I believe are the co2 bubbles migrating through the filter
By them being sucked into the filter the co2 is not doing its job

 

Might have something to do with the position and direction of your outlet? If you get effective circulation throughout the tank you will get effective CO2 dispersal. I use the same method with a Fluval 406. I also have a secondary filter plus powerhead to help with circulation.

 

My recommendation would be to stop doing this setup. 1) Bc of the airlock/burping effect and the possibility that its prematurely wearing out your impeller and 2) something is goin on inside your canister b/c as you said, it's not dispersing as well as it used to....so maybe again, something tied to your impellers function. But it could just be something as simply as you needing to clean your filter/pads bc the flow has diminished, and thus co2 dispersal has dropped.

My recommendation is to run everything inline with a co2 reactor or diffuser. Yes, its completely possible with fluval canisters...i do it myself with my 307. Remove the crappy ribbed hoses that fluval gives you, and replace with 16/22 hoses. I prefer the eheim 16/22 hose because I find them the ideal rigidity. Heat up the hoses by dipping them in cups of boiling water, and once softened, slip them over the canister's exit port. Use a worm-gear hose clamp to ensure that it never slips off. Here's a photo of my setup. You get all the benefits of your current setup, without the wear and tear on your canister's impeller.


Please note, I have since revised this setup and have shortened the green 16/22 hose that runs between my canister and my co2 reactor. I was losing way too much flow with the length that's pictured. You can expect to lose some flow with a reactor though...no real way around it. Also, once you make the switch from fluval's stupid ribbed hoses, you can run glass lily pipes on the outlet side.

 

I’ve tried inline but did not like the flow reduction or the misty look in the tank. I’ve never noticed any increased wear on the impeller.

 

I’ve tried inline but did not like the flow reduction or the misty look in the tank. I’ve never noticed any increased wear on the impeller.

I agree, inline will definitely reduce flow. I countered this by buying the next step up in filtration (my tank really only needs the filtration capacity of a 207, but I went up to a 307 in anticipation of flow reduction from my inline reactor and inline heater.)

I don't get the soda pop mist when I use a reactor (vs say, a diffuser). I get more mist from my plants photosynthesizing than I do from excess undissolved co2. A diffuser on the other hand will definitely make your tank look like 7-up.

Lastly, I don't pump co2 into the intake of my canister filter because I worry about co2 being mixed within the contained chamber that also houses your beneficial bacteria. Not sure if i'm overthinking it, but the subject of bacteria inside the canister filter being harmed by co2 (and affiliated ph drops and decrease in oxygen, etc) has been debated quite a bit online, so I just try to play it safe just in case there is some detrimental effect.

All this being said, I do run my co2 directly into my intake on my HOB filter that I use for my 3 gallon shrimp tank, bc that filter was dirt cheap and I'm already playing with fire with co2 injection on such a small tank.

I have my CO2 diffuser directly under my Fluval 207 Canister Filter intake and all the bubbles can be seen going into the intake. My drop checker does not really go as green anymore, as it was before when I used the flow of water to disperse the bubbles.

Also, something I've noticed is that after the diffuser turns off, the canister can be heard to make loud "burps", which is normal for this setup but I notice it's only happening after the diffuser stops letting bubbles out into the intake.

I'm wondering if I'm missing something here, as people online said diffuser under intake is a good idea, I'm not seeing better results. I've thought to use an in-line diffuser but I'm not sure how to go about with the ribbed hose the Fluval canister provides.

I reread your initial post. If your canister is burping even though the diffuser is already off...that means your canister is still working out the excess co2 that's built up inside it. That means that you're injecting co2 into the intake at a high enough rate that not all of it is being fully dissolved by the impeller and that there is a "bubble" of built up co2 inside the canister. In other words, your canister is not dissolving 100% of the co2 that's entering it.

 

My recommendation would be to stop doing this setup. 1) Bc of the airlock/burping effect and the possibility that its prematurely wearing out your impeller and 2) something is goin on inside your canister b/c as you said, it's not dispersing as well as it used to....so maybe again, something tied to your impellers function. But it could just be something as simply as you needing to clean your filter/pads bc the flow has diminished, and thus co2 dispersal has dropped.

My recommendation is to run everything inline with a co2 reactor or diffuser. Yes, its completely possible with fluval canisters...i do it myself with my 307. Remove the crappy ribbed hoses that fluval gives you, and replace with 16/22 hoses. I prefer the eheim 16/22 hose because I find them the ideal rigidity. Heat up the hoses by dipping them in cups of boiling water, and once softened, slip them over the canister's exit port. Use a worm-gear hose clamp to ensure that it never slips off. Here's a photo of my setup. You get all the benefits of your current setup, without the wear and tear on your canister's impeller.


Please note, I have since revised this setup and have shortened the green 16/22 hose that runs between my canister and my co2 reactor. I was losing way too much flow with the length that's pictured. You can expect to lose some flow with a reactor though...no real way around it. Also, once you make the switch from fluval's stupid ribbed hoses, you can run glass lily pipes on the outlet side.

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Thank you! I might just do that, I have my in-tank diffuser right now put in another location where the outlet of the filter pushes the bubbles around. Makes me need at least 3bps for my 40 gallon long. Wondering how much better the inline diffuser would be.

Do you think I can get away with using regular 16/22mm tubing from Home Depot and not Eheim specific ones?

I’ve tried inline but did not like the flow reduction or the misty look in the tank. I’ve never noticed any increased wear on the impeller.

How much flow did you use and was the inline a lot better at dispersing the co2 at least?

 

Thank you! I might just do that, I have my in-tank diffuser right now put in another location where the outlet of the filter pushes the bubbles around. Makes me need at least 3bps for my 40 gallon long. Wondering how much better the inline diffuser would be.

Do you think I can get away with using regular 16/22mm tubing from Home Depot and not Eheim specific ones?

How much flow did you use and was the inline a lot better at dispersing the co2 at least?

It seemed like about 20%-30% flow reduction but hard to say. Dispersal was much the same, possibly better through the canister since there is no flow reduction and I find that it diffuses into the water almost as good.

 

Thank you! I might just do that, I have my in-tank diffuser right now put in another location where the outlet of the filter pushes the bubbles around. Makes me need at least 3bps for my 40 gallon long. Wondering how much better the inline diffuser would be.

Do you think I can get away with using regular 16/22mm tubing from Home Depot and not Eheim specific ones?

How much flow did you use and was the inline a lot better at dispersing the co2 at least?

If its pretty cheap at home depot, it might be worth a buy, otherwise I would get the Eheim stuff off amazon etc. That said, the only problem with some of the cheaper pvc stuff that I've seen at Home depot is that it's really soft and kinks (think garden hose) if the tubing has to go through tight bends. You can always alleviate any kinking by supporting that area that is folding with a either a ziptie or hose clamp, so that it reforms the shape of the tubing to be circular. If you decide to go inline, I would highly highly recommend getting a reactor instead of a diffuser. You will get better co2 dissolution and efficiency with a reactor and you won't have to deal with the fizzy look of co2 bubbles all over your tank. I use the Sera Flore 500 reactor for my 40 gallon. I stick a bit of sponge foam and biomedia in the chamber to help beat the bubbles up and assist with extra dissolution of the co2.

 

kc: What size hose fits in the Sera Flore 500 reactor?

 

kc: What size hose fits in the Sera Flore 500 reactor?

16/22mm fits. Heat the tubing by dipping it in hot water before hand. Use worm gear hose clamps...rumors and reviews have stated that the connections leak without them. You might also need to use plumbers tape on the threading of the sera reactor.