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DIY CO2 Guide with Pictures & Recipes

384050 Views 158 Replies 69 Participants Last post by  Gor22don33
DIY CO2 is a matter of taking Yeast and Sugar, and mixing them with water to create a reaction by product of CO2 gas. This works extremely well for 1-30 gallon tanks. For larger aquariums you must use more DIY bottles to increase CO2 output. It requires more effort, and most tend to go over to pressurized because the time and effort, and added cost over time required. But it can be done.

1. Gatorade, Apple Juice, or Oceanspray Bottle
2. 2 Cups of Sugar
3. 1/4-1 teaspoon of yeast
4. 1/4 teaspoon of baking soda (optional)
5. Diffusor: Hagen Ladder, sweetwater AS10, or through filter intake

1. 2 Cups of Sugar
2. 1/4-1 teaspoon of yeast (more yeast = faster reaction = more CO2 for shorter time (2+ weeks))
3. 1/4 teaspoon of baking soda (optional)

Making the Canister (Reaction Bottle):
1. Take drill bit or hammer and a small nail (smaller than the diameter of tubing).
2. Unscrew your cap, hammer/drill the nail into the cap to make a small hole
3. Get some Airline tubing and pull it through the small hole with pliers.
4. The small hole will create a seal around the tubing so no need for glue, hence the extra small hole.

Adding the Recipe:
1. Add 2 cups Sugar
2. Fill the container with water up to 3/4 way.
3. Add 1/4-1 teaspoon yeast
4. Add 1/4 teaspoon (baking soda)
5. Put the cap on and twist it on tight.

Diffusion Methods
1. Line directly into the intake of your filter,
2. Limewood Diffuser
3. Sweetwater stone AS10
4. Hagen ladder
5. Glass difusser

Wait a few hours and you got CO2

Special Notes:

Check Valve Prevention System + Yeast Strainer
In order to keep the Yeast Muck from being released into your tank, A bubble counter or separator is used to catch the muck. This DIY bubble counter also provides a check valve system to prevent water from back siphoning out of the aquarium.

A Syringe from Rite Aid, Long Drugs, Walgreens, etc, can be paired with a standard plastic check valve to make this DIY bubble counter.

1.Take the plunger off
2. Add some glue to the check valve
3. Insert check valve and dry for 24 hours.
4. Once dry, the tubing will fit on the end of the check valve, and at the end of the syringe nozzle.
5. Insert this between the diffuser and your reaction bottle.

NOTE: Some plastic check valves occasionally don't work, always check your valve when replacing the DIY CO2 mixture. CO2 will degrade plastic valves over time, so always check.

For Larger Tanks
For larger tanks, and those that need to lower the ph more with more CO2 output. Using multiple diffusers placed at each side of the tank (left, right, middle, etc) will increase CO2 dissolution. In addition, you can add a T-valve to connect multiple bottles and to own diffuser to produce more out of your diffuser. Here is an example. Placing the diffusers under a current will blow the CO2 around and further increase CO2 dissolution and contact time with the water.

Is it working?
You should see bubbles coming out within 4-24 hours. To see if your CO2 is being properly dissolved based on whichever diffusing method you chose, test your Ph before adding CO2, and after adding. You will see a drop. Refer to a PH and KH chart to see what your levels are at in ppm.

This reaction will last at least 2 weeks to 4 weeks. The more yeast added the faster the reaction but shorter duration.

Be careful, and enjoy your CO2.

-John N.
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Syringe Bubble Counter

Check valve goes like this: 2L juice bottle - tubing -check valve-syringe - tubing to diffuser inside tank.

The check valve should go in the direction that allows CO2 gas from bottle to enter the aquarium. You can blow through it to make sure it's facing the correct way.

The tubing will fit directly on the syringe output and also on the check valve, so no glue is needed there. Only glue is needed where the check valve and syringe connect.

(picture from a member on another forum).

Either tubing will work, silcone will get brittle over time, normal vinyl tubing will get harder over time. Both will need replacing once you see that it does or they system starts to leak CO2. This time can be a period of 3+ months before needing service.

-John N.
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Hi Upikabu,

No problem, the guide was something I looked for when I started, and I was having a hard time grasping the concept, so pictures definately help. And so hence the creation of this guide to help others.

As for your questions, I do stir my sugar and try to dissolve some of it when I start. I never did it with hot water, just luke warm. I noticed a slight increase when it first starts, but it the bubble count balances out over time.

You'll get a better output of CO2 if you use a larger bottle.

Shaking: It helps, since it's dissolving and mixing up the sugars and yeast. But again, it doesn't make a noticable difference in the long run in my experience. I don't recommend it since the liquid can hit the inside tubing, and get some yeast muck in your tubings.

As for the baking soda. It's to raise the KH and stabilize the reaction if you have low readings of KH in the water you are using. I stick a little in there, every time, since I have a KH of about 3.

My advice try it without baking soda, and once with it, and see if you notice a difference. It doesn't hurt the reaction.

-John N.
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Depends on your reactor diffuser method. I've gotten 20 ppm using a hagen ladder with 1 bottle, when I used two I got about 35 ppm.

-John N.
For the Hagen Nutrafin Canister:

Sugar to the bottom inside line,
Water to the top inside line,
1/8-1/4 teaspoon yeast
1/4-1 teaspoon baking soda

Close as tight as possible and enjoy.

The placement of the hagen should be under good circulation as to spread the dissolved CO2 around, and maybe catch the escaping bubble. Not to worry about catching that bubble, since the bubble gets about 85-95% smaller as it travels the rungs, giving you very good dissolution.

-John N.
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For me using the above recipe in the nutrafin canister, it lasted for about 2-3 weeks. It probably could go longer, but I like to have it going at the peak performance.

Using a Juice or 2L bottle, the reaction and bubble count was longer at about 3-4 weeks.

-John N.
Jimbo for the CO2 bell, it really can be anything that can create a dome where CO2 can fill in. Commonly used items would probably be small bottle soda tops adhered to a weight, glass sauce dishes, etc.

-John N.
harbisgirl said:

I'm new, forgive me if this is a ridiculous question :)

I have a sand substrate, would it work to stick the tube under the sand to diffuse the bubbles?
Interesting idea, but probably no, since a large bubble will still come out of the sand and rush to the surface. The key for getting CO2 in your tank's water is to have the CO2 gas bubble in maximum contact with the water so that it can dissolve. For example, the hagen ladder does this very well. The bubble travels up the ladder getting smaller as it goes up. Similar to this type of glass diffuser that New Guy has. See the cool video in post #10 of

Other options is to have the impeller of your filter or powerhead chop up the bubbles. So feeding the line directing into the intake of your filter wlll maximize the surface area of the tiny bubbles that get chopped up, and provide better chance of dissolution.

-John N.
It's really all dependent on how much yeast and sugar is supplied in the bottle. Since the 2L bottles types can hold more of both, the reaction will be last longer, and have a higher production rate in the short term (2 weeks) if supplied with more yeast (3/4 tsp).

You'll see an longer reaction, and increased CO2 production if you switch to the 2L bottle, and add a larger amount of yeast than recommended. This will shorten the life span of the CO2 from 3-4 weeks to 2 weeks, yet production will be dramatic more.

As Sean stated, wine yeast will also enhance the life of the reaction.

I recommend using (2) 2 liter bottles T-ed together for maximum CO2 production.

-John N.
I've used standard Epoxy Glue without adverse problems. But I've used silcone glue with positive results but after a few months the silicone will need replacing placing.

You can also try a DIY Separator Bottle

Much like Mikee's DIY Separator Bubble Counter:

-John N.
viviparu' said:

Let's assume that ideal for my aquarium is to have and addition of 15 ppm of CO2. My question is: how many bubbles/second that means. I have a bubble counter and I want to set the number of CO2 bubbles released in one second in the tank in order to have 15ppm CO2 addition. So: 15ppm of CO2 means how many bubbles/second?

Unfortunately this translation isn't as simple as that. PPM cannot be converted in BPS (bubbles per second). Each system will be different, see the CO2 Charts in the fert section to see how the drop in pH is effected by each additional bubble to get this rate.

In general I would say that most DIY CO2 setups will produce on average 15-20 ppms. The better setups with mutliple bottles will yield even more dissolved CO2 levels.

-John N.
The silicone may hold, but may have leaks later as things bend and break their seal. Use a small amount of normal epoxy glue. Or you can just do the separate Bottle bubble counter as it might be easier to make without the extra glue or silicone.

As for the Spio diffuser, the length of it might be distracting in a 10 gallon tank. However I am sure that it will work like any of the other types of glass diffusers. I use the Aquabotanic's Might Mini often switched out between cleanings with the Aquaticmagic's nano glass diffuser in my 10.

-John N.
As suggested in my earlier PM to ya, check for leaks around the cap area, and make sure the yeast is still good. Since you're not using a glass diffuser or anything at the end of your airline tubing, we can take out the lack of pressure to run those items out of the equation. That leaves us leaks and bad yeast.

You can test the functionality of the yeast by putting it in a coke bottle and sealing it aff completely. It will pressurized the coke bottle in a few hours indicating that Co2 production is occuring and the yeast is good. And you can check for leaks around the cap with a soapy solution to look for soapy bubbles from the leaks.

-John N.
If the bottle is seal off completely, the bottle will get harder and harder to squeeze because the yeast reaction creates CO2 gas that will fill up the open air space. This tells you the yeast is still working because it's making the gas.

Once you figure that the yeast is good, you can proceed to figuring out if you have leaks.
This is the way I would do it.

1. Mix the ingredients in the bottle.

2. Cap the bottle with the cap with your airline tubing through the top of it

3. Tie off the end of your airline tubing, so that no gas can escape.

4. Make some soapy water (make it similar to the toy bubble blowing solutions)

5. Take that solution and wipe it around the connection (cap area) and see if there's bubbles coming from those areas. In addition, since the tubing is tied, the bottle should feel pressurized (hard to the touch) indicating no leaks.

Once you figure out you have no leaks, and that the yeast is working, you are good to proceed.

-John N.
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That's normal as it starts up. It will be erratic, and then will be constant, shooting out 1 or 2 bubbles every 4-5 seconds.

This takes about a day or two, and after that, it will be constant for about 2 weeks, and then will become erratic again as the yeast eats up all the sugar. That means you should being to replace it.

-John N.
Yes you probably won't need a pump. DIY CO2 doesn't usually produce enough CO2 that will harm fish or inverts. However if you feel more confortable, you can run an airpump at night on a timer to oxygenate the water.

-John N.
I would be weary connecting the CO2 line directly powerhead using the venturi section because it typically sucks in air. When connecting the CO2 line directly you run the risk of having your yeast mixture getting sucked up into the powerhead and into your tank.

I would instead simply stick and wedge your CO2 tubing in the intake of your powerhead so that it will suck in and break down the bubbles coming out of the tubing.

-John N.
Ah, I see where you're going. It looks good. I'm having trouble seeing in the picture where you are sticking the CO2 line, inverted and centered in the clear tube with blue top? It looks like it'll work, keep us posted on how effective it is.

-John N.
It sounds like your the CO2 is being dissolved properly in your set up. A tell tell sign is to watch your pH drop by measuring the before and after.

In regards to fish gasping, DIY CO2 usually doesn't create that many problems, but it sounds like an airstone is needed in your case to get that needed dissolved oxygen in the water column.

-John N.
Yup, you are correct. The bubbles produced from the mixture contains near pure CO2 gas that is readily dissolved in water. However, since DIY CO2 doesn't usually produce a high amount of bubbles the amount of CO2 dissolved isn't very high.

Because of the surfacing fish,

The problem could be:

1) Too much CO2 at night when lights are out. Plants and DIY CO2 producing CO2.

2) Too low O2 at night when lights are out. Plants no longer producing O2.

Suggestion: add airstone at night on a timer.

-John N.
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