Inline Co2 With Fluval Canister Filters?

Rob McFarland

New Member
Dec 18, 2018
Spokane, WA
Hi everyone! First post here, please let me know if I've done anything wrong.

I have a Fluval FX4 and Fluval 206 and I would like to add inline CO2 diffusion to both tanks (currently using pollen glass diffusers. The intake/outtake hoses of the Fluval filters are ribbed, which to my knowledge, doesn't work well with inline diffusers. Any light you can shine on this for me in terms of what specific gear I need to make this happen would be greatly appreciated. Thanks in advance!


Lifetime Members
Lifetime Member
Aug 25, 2016
Hello, and welcome! You don’t need any special gear to install an inline diffuser if you have vinyl piping, basically get yourself two per tank, keep one cleaned and on reserve for when you need to change it out (every few months) and put the new one in. In regards to the ribbed piping, maybe you switch over to vinyl for the parts that attach to the diffuser, most inline diffusers use a compression type joint, so you’ll need a smooth flexible pipe in order to install them. I found a couple thread on the planted tank talking about switching things over. And sounds like a combination of barbs and hose clamps for a hardware store. I’ve never worked with fluval piping myself. The diffusers really don’t impact pump output at all. I personally would only install them on my outflow piping. I have the Atomic branded ones from green leaf aquariums. There are many versions, I’m sure they are mostly the same.

Couple things I don’t like about them. Say you install the inline diffuser close to your pump, by the time the time your bubbles make it to the tank they will have congregated together into big bubbles that immediately go to the surface and pop, wasting the CO2. Not all the bubbles, you’ll still have lots in the tank, but I noticed this minor detail. If I was to go back to inline diffusion I would try to install it so the atomized bubbles don’t travel through as much piping, keeping them smaller. The second thing you will immediately notice is reduced visibility in your tank, there will be so many bubbles that you won’t see your plants as clearly. Initially this didn’t bother me, but I kept noticing how nice things looked when the CO2 wasn’t on. I also noticed that there were so many bubbles my pumps would make that noise they make when they are pushing gas through the impeller, but more frequently. I have my tank in my bedroom, and hours after the co2 was off the filter pump would be making noises, cutting up gas that had built up in it over the day.

There are lots of ways you can do your CO2. I ended up keeping my inline diffuser but I use it to feed a Sera 1000 reactor. I still get a bit of CO2 misting, but it doesn’t take away from the view of my plants. Video of setup here Further up in that thread there is more discussion about CO2. If you do decide to go this route make sure your pump is strong enough, mine is just barely, but I think it might have more to do with my fine prefilter sponge, but I’m in the process of changing it out. Another member uses an inline diffuser to feed his reactor as well with good results.
Last edited:

Dmytro Shevchenko

New Member
Jan 14, 2019
Wilmington, DE
Fluval maked ribbed hosr adapters, about 10 dollars a pair. Two size fluval hose I think along with 2 size in line diffusere. Atomic, UP aqua, and a new aluminum plastic one from GLA which is on amazon also. The aluminum one is the strongest but I couldn't get the adapters it came with to accept the fluval hose adapters so I used a plumbing clamp.
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