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How to make a DIY CO2 diffuser


SamH

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Today I made my own CO2 diffuser adapted from the 100% diffuser method. Although the CO2 doesn't completely dissolve into the water, only very small bubbles escape. This costs very little to make from things you probably have lying around the house.

Materials needed

1x plastic bottle

1x filter with an outlet tube/pipe

1x length of airline

1x DIY CO2 setup

Tools needed

Drill and/or soldering iron

Pliers

Scissors

Method

1. Find a plastic bottle (preferably clear) and cut the bottom off it.

2. Remove the lid and make a hole slightly smaller than your filter outlet pipe with a drill or soldering iron. Also make one either in the lid or by the curve of the bottle slightly smaller than your airline tubing.

3. Make one hole near the top and one hole near the bottom of the bottle that is slightly smaller than the diameter of the clips of the suction cups.

4. Push the clips through from the inside so they attach to the suction cups on the outside.

5. Cut the end of your airline tubing (coming from your DIY CO2 bottle) on a 45° angle or steeper and push it into the hole made for the airline tubing. Thread it through as much as possible, pull the rest through with pliers until you have around 3cm of solid airline tubing in the bottle. Cut off extra if necessary.

6. Also cut the end of your filter outlet if possible on a 45° angle or steeper and push it into the hole made for the filter outlet in the lid of the bottle. Pull it through with the pliers as you did in step 5.

7. Attach the bottle to the side of the aquarium and get rid of any air trapped in it. Tilt on an angle if necessary, try to have it as close to vertical as possible. This will stop more bubbles from escaping, providing better diffusion.

8. Turn on filter and watch as your CO2 builds up inside the bottle. Eventually the trapped CO2 will come into contact with the flow from the filter outlet and be churned in with the water. Some micro bubbles may escape, this is fine. If any larger bubbles are escaping then your diffuser isn't on a steep enough angle or you have too much CO2 in your diffuser, the latter is nothing to worry about.

Here are some pictures of the CO2 diffuser and setup I made earlier today. CO2 from two 3L juice bottles built up very quickly, around 3bps+.

Two 3L bottle filled with 2 cups sugar, 1 tsp of yeast and the rest (up to the curve in the bottle) with warm water next to an Eheim 2213 canister filter

IMG_6232.jpg

The airline and filter outlet attached to the diffuser

IMG_6233.jpg

Diffuser above Jager 100w heater. Note the small bubbles on the right escaping

IMG_6229.jpg

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nice, but why dont you just use a frit diffuser? 2 cm in diameter as opposed to having a massive bottle in the tank?

Because they cost close to $20 incl. shipping and I have no job. This cost me about 30mins of my time and an $0.89 bottle of soda :wink:

what is the noise level like with water sloshing into the tank? :-? or is it not sloshing?

Gee thanks, now I notice it :lol: It's almost nothing when standing at a normal distance from the tank, but when I put my ear up to the glass it's just the same as water flowing from 3cm above the surface, pleasant even 8)

realy cwl :hail::bow::hail::bow:

Thanks, one bow and one hail is heaps :wink:

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What happens when too much CO2 builds up? does it pull the bottle to the surface more or does it escape in big bubbles out the end.

It starts to float the moment CO2 enters the bottle, the more CO2 the higher it floats. I have larger bubbles escaping every now and again, mainly micro bubbles though. In theory most of the CO2 is mixed into the water rather than expelled as bubbles.

Tap into the outlet pipe of the filter for your CO2 feed.

That was my first idea but I wasn't sure how secure it would be. Also worried about leaks from the pipe.

Inlet would be better but you may get a airlock.

Also another one of my first thoughts, but it's bad enough already without adding anything to it. Air seems to get caught in the filter anyway, I'm not going to add CO2 especially as it's in the lounge.

Thanks for the suggestions though 8)

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Also another one of my first thoughts, but it's bad enough already without adding anything to it. Air seems to get caught in the filter anyway, I'm not going to add CO2 especially as it's in the lounge.

Wouldn't it diffuse better if you put the CO2 carrying airline into the intake of your filter?
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Nice! My bro-inlaw had a similar setup, used a old school glass coke bottle instead, had the neck faced down and the outlet and co2 line feeding up through the neck. The flow from the outlet made the trapped co2 swirl like crazy, the force just pushed the water(now fused with co2) back out the neck.

Wouldn't it diffuse better if you put the CO2 carrying airline into the intake of your filter?

I have mine fed into the intake of a hang-on type, ive had it airlock a couple of times but its ok now, but as mentioned it can make a lot of noise when the bubble hits the impeller.

May I make a suggestion, as its so cheap to remake these types of DIY diffuser, dont cut the bottom of the bottle, instead drill HEAPS of tiny holes in the bottom, enough for the water to still flow freely. Closing the bottle will allow to make more of an internal underwater reactor that you can see working, and any big bubbles that make it to the bottom will push through the tiny holes making them tiny bubbles.

:bounce:

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Wow, that's an awesome suggestion :hail::hail:

I'll have to try it when I get a spare bottle.

Thanks!

YW :)

Also I added a Airline control valve, the ones ya get to control amount of 02 bubbles (in this case c02), between the tank and yeast/sugar mix, it does build up a lil back pressure, but not enough to cause an explosion. In my case its let me control/regulate the amount of bubbles going into the tank.

My setup:

Mix Bottle - Gas Separator - Airline Control Valve - Tank

co2small.jpg

HTH

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