# Co2 diffuser under gravel = better diffusion?



## shift (Dec 21, 2012)

I just had a thought. If one was to burry the diffuser under the gravel. Wouldn't it further diffuse the bubble and prevent algae buildup since its not seeing light?

Has anyone tried this?


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## 77_Bus_Girl (Dec 30, 2012)

Never tried it but assume it would just collect into larger bubbles quickly and bubble straight up to the surface. 

Sent from my SGH-I727R using Tapatalk 2


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## shift (Dec 21, 2012)

Hmm that would defeat the purpose. Okay scrap that idea



Generally how long do you find is the ideal time for bubble stay under for until they reach the surface?

I know longer is better but so far 20-30s is the best I have achieved


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## monkE (Aug 4, 2010)

i think the bigger question is how large are the bubbles when they reach the surface compared to when they come out of the diffuser 


my ceramic diffuser was great for making such small bubbles immediately that they were almost completely dissipated by the time they reached the surface


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## effox (Apr 21, 2010)

The goal is just to get them as small as possible before they reach the surface if you're using a diffuser. After playing with positioning, you'd just dial in the co2 based on a drop checker at that point.


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## shift (Dec 21, 2012)

Which diffuser have you found to give the smallest bubbles


The one I have is letting out a few streams from the edges rather than dispersing them through out. I'm half debating super gluing the edges to force it to come out of the center. 

The bubbles take 20-30s to reach the surface but I don't think the size changes to much


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## monkE (Aug 4, 2010)

shift said:


> Which diffuser have you found to give the smallest bubbles
> 
> The one I have is letting out a few streams from the edges rather than dispersing them through out. I'm half debating super gluing the edges to force it to come out of the center.
> 
> The bubbles take 20-30s to reach the surface but I don't think the size changes to much


i was using a fluval ceramic disk... worked quite well for me but got glogged up and needed cleaning regularly


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## effox (Apr 21, 2010)

I'm using a DIY internal reactor. It's far less attractive and sleek looking as a ceramic diffuser, but works better. I can see some fine bubbles make it out at times, but they just disappear rising near the top of the tank. The powerhead probably helps the circulation of the co2 as well.


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## gklaw (May 31, 2010)

Wood airstones used for SW skimmers make the finest bubbles I have seen. That's why they use it for skimmers.
Unfortunately buying them at LFS cost a few $ and they do deteriate. More fortunate if you are handy, you can buy the wood from Windsor and make them yourself. Could be made for say waaay under $1 each.


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## Tn23 (Apr 21, 2010)

use an inline reactor if you are using a canister filter. The bubbles are soo thin they are almost not noticeable and get spread throughout the tank evenly. I purchased mine from Jiang604 a year ago, not sure if he has anymore. Best I've used and I know some of the other pros on this forum use them as well.


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## shift (Dec 21, 2012)

So to build a co2 reactor you inject co2 and water in the top and the flow exits through the bottom of the chamber Since the co2 is injected at the top it must dissolve or be forced down the tube to escape. Is this correct? Would one want to use an air-stone diffuser inside the reactor or just strength co2?


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## effox (Apr 21, 2010)

An in-tank reactor is a chamber with one sealed end on the top and an open end on the bottom. The co2 tube (rigid so it doesn't flail around) goes through the sealed top and almost the bottom of the open chamber so the release co2 rises to the top of the chamber. It gets mashed around by a powerhead that is sealed to the side of the chamber, which pushes water through the chamber, and eventually the co2 is redistributed and leaves the chamber almost fully exchanged in water.

Here's a pic of the one I built a few weeks ago:








If you're doing co2 on your tank with the fx5 you have, use an inline reactor, as it won't take up tank space.

A inline reactor (more expensive) will look like this, commonly filled with bio balls:








Another form of inline reactor, which is one that I used in the past is called an atomizer ($20-30 and still very effective):


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## shift (Dec 21, 2012)

I think I may build an inline one for the fx5


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## trout (Mar 21, 2012)

if you dont end up going inline, i'd recommend the bazooka/atomic diffusers. best ive ever used, tons of micro bubbles 360' vs a standard glass diffuser.

i think canadian aquatics have them


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## shift (Dec 21, 2012)

I'm currently in the hardware store building.. Any suggestions for what to use as the co2 injection barb?


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## effox (Apr 21, 2010)

It'll be a 3/16" fitting that you'll be looking for. You'll probably be able to find a barbed brass fitting in the same plumbing isle.


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## shift (Dec 21, 2012)

Hopefully brass is okay because this is all I can find. Will co2 bubbling in from the side do the job or should I find. 2 way baby and have a airstone internally


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## effox (Apr 21, 2010)

Brass contains copper, and the fitting would be submerged in water, but I haven't heard of anyone here stating that copper leaching from brass would have noticeable effects on tank inhabitants.

It depends on how you are going to plumb the reactor. The co2 will need to inject from the opposite end of the outflow. Ideally you would have a line fitting on the top of the canister\pvc, with a tube connecting from there to the bottom, where the filter's output would connect. You could otherwise plumb the outflow to the top, increase the filter's tubing from the bottom to your tank's spray bar.

Either way I'd recommend having it on top and not on the side as all designs I've seen are like this.

I don't see any need for an airstone if you design the reactor effectively, especially since it would deteriorate or become slimed up and require regular maintenance.

I'm not sure where a 2 way baby valve comes into play. I just used a check valve to ensure water pressure didn't come up the line.


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## shift (Dec 21, 2012)

So canister to top of pipe. Outflow at the bottom. You think injecting co2 into the angled reducer is the best spot?


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## effox (Apr 21, 2010)

From the fittings I see you using, yes I'd put it at the top angled reduced.


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## shift (Dec 21, 2012)

Thank you sir. It sound like a plan. Should I be adding in a check valve


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## effox (Apr 21, 2010)

Definitely add a check valve to the co2 tubing. When your pressure is off, ie turning it off at night\solenoid or getting the tank filled, the water can run up the line.

Take some pics of the build along the way to post in the DIY section. Showing the parts needed is already half the effort, and I see the majority of them in that picture you posted already


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## shift (Dec 21, 2012)

I will have to squeeze it into the back corner... But what so you guys think of this design. Any critiques before I glue it up?


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## effox (Apr 21, 2010)

I wouldn't glue the end caps on, so you could get access to the inside, but it looks good to me. Hopefully the two 90 degree turns don't impact much on water pressure.

The only thing I would do is load it up with bioballs to chop up the co2 as it circulates around since it's a top to bottom design, as opposed to feeding in from the sides of the pipe which creates more of a circular flow of water.


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## shift (Dec 21, 2012)

Or design #2









The only issue I see with injecting it from the side rather than the top... wont you get an air bubble trapped at the top?

Second Question for either design.. is it better to inject the co2 at the top or bottom of the reactor?


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## effox (Apr 21, 2010)

If that becomes an issue, you can add a return loop from the top of the pvc that goes back into the outflow of the 3/16" connector. I'm not sure what fitting you would you use for this.

I've added a return loop\burp valve or whatever its called on my internal reactor, but it's been effectively distributing the co2 with the water so I don't see the need for this. It would depend on the flow of water and injection rate I suppose.


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## shift (Dec 21, 2012)

Does my CO2 line need a check valve?


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## shift (Dec 21, 2012)

I finished building my reactor.. the only issue is when the FX5 "burps" it self it dumps a bunch of bubble into the reactor.

So far with the CO2 is off and there has been no water feeding back into the line.. but i will put on a check valve anyways for piece of mind

I can see a bunch of air bubbles coming out of the outtake.. I'm sure they will dissipate over time.. I havent turned the CO2 on yet as i'm waiting for the air bubbles to disappear first


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## shift (Dec 21, 2012)

So with the CO2 on it looks like i'm getting a bunch of micro bubble coming out the out flow.


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## effox (Apr 21, 2010)

Did you try filling the reactor with water first, just incase there was trapped air somewhere in the line?

I'm not really sure why that is happening without co2 even being injected.


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## shift (Dec 21, 2012)

I turned the FX5 outflow down a bit and the bubbles are now much smaller.. I also directed the outflow bubbles more down/across the tank rather than to the surface.. and it seems to look a little cleaner and not a whirlpool of bubbles.. (much smaller with the filter turned down a notch or two)

I think the CPD's apreciate less flow and I can still see every leaf/steam in the tank moving (although some are very slight)... i think i'm good!

I took a bunch of pics along the way, so i will have to do a little write up later once its fully tweaked.


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## effox (Apr 21, 2010)

The only issue with seeing bubbles (besides the visual distortion of your tank) is that it means the co2 isn't mixing as effeciency as it should. 

I'm confused exactly as to why this is happening. I didn't have this issue with my canister, I just had to prime the heck out of it so it would work right.


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## shift (Dec 21, 2012)

Actually once i turned it down the flow i started to barely see bubbles.. Now they may have been air still trapped in the reactor.. but now it seems almost clear. Just the odd bubble every five seconds or so 









So the trick seemed to be dialing the flow back. i suspect if its was 4-5" taller it wouldn't be an issue.


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## shift (Dec 21, 2012)

Is lime green the ideal color for the drop checker? I'm assuming I need to increase my bubble count a bit


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## effox (Apr 21, 2010)

I'm pretty sure a little lighter green than what is pictured is at optimal level. Darker green indicates that it's slightly insufficient levels.

It's hard to tell with pictures and it depends on the tank lighting, but it looks a little dark.

Glad your reactor works well after you dialed the flow back.


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## shift (Dec 21, 2012)

I just upped the bubble count slightly so ill see if the color changes is the next little bit


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## shift (Dec 21, 2012)

How's this looking for drop checker color 








It's darker when viewing through the side but the suction cup acts as a lighter background


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## effox (Apr 21, 2010)

You want it lighter than dark forest green, but don't want it lighter than lime green.

I've read it's best to check it against something white. I know if I look at mine at different angles\light conditions the shade changes.


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## Reckon (Jul 25, 2012)

I personally think for low co2 injection, ~ 15-20ppm that green is about right. I have that in my 30gal low light collectoritis tank and for the most part even my higher light loving plants stay alive (once in a while they'll autofrag though). Your plants will probably be growing nicely with that amount. You can go with that for a month and then see if you want to push more CO2.


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## shift (Dec 21, 2012)

Sounds good. Thanks Reckon


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