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DIY CO2 Issue

2994 Views 26 Replies 12 Participants Last post by  acmarauder

I have a Hagen Nutrafin CO2 system using sugar and yeast. I add one cup of sugar and 1/3 tsp of yeast and it only lasted me 3 days.

What's going on? Less yeast and more sugar would make it longer, but that means less CO2 output.

What's the best DIY CO2 system out there?

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I'd say the best DIY system is an actual DIY system. Those store-bought things are silly. Just make a 2-liter set up. You can connect two 2-liters and a 20 ounce bottle for a bubble counter / catch basin.

If you add a pinch of baking soda it helps.
What do u use to seal the cap after you drilled a hole on the cap?

Basically you have to mix eveything in a bowl and pour them into the bottle?

I thought baking soda is to prevent PH drop in the tank?
Just follow the instructions for the nutrifin. Put sugar up to the first indicator in the bottle and fill with water to the 2nd indicator. It roughly measures out to 1/3 cup sugar and 2 cups water and then add 1/8 teaspoon yeast.
What kind of bottle do you use? 2 or 3 liter soda bottle? Or the original Hagen container thing?
The 2 liter coke bottle. I know I need to install a fitting on the cap to attach to the tubing. But I dont know what to use and seal it to prevent CO2 leak from the drill.
There is a thread that details it, but an 11/64 drill bit (drilled from bottom of the cap to the top) will seal air tight without any silicone or glue. Simply cut the end of the airhose to be pulled through the cap at an angle so it fits into the hole enough to grab the other side with pliers or tweezers or whatever you have handy. This will seal airtight, I have tested it on every bottle and no leaks just try not to wiggle the drill bit side to side much.
I use aquarium silicone to seal around the tube. The baking soda prevents a ph crash inside the bottle which kills off the yeast. Definitely check out some of the threads on DIY CO2. I'm sure there are some with detailed instructions.
The tubing diameter is 1/4", so drill with a smaller bit than a 1/4" through the top of the cap. Cut the end of the CO2 tubing at a sharp diagonal, so you can slip through one tip, grab it with tweezers, and pull the tube through.

I'd use alot more sugar and yeast too.... I use a 2L bottle (a soda bottle that naturally contains CO2) and add 2 cups of sugar + water to about 2/3 full. Then mix up 1 teaspoon of yeast and a bit of water. Wait 10 minutes, and then dump the yeast water into the 2L.

I run two of these on my 55 gallon, and maintain right at 30ppm levels. Replace them about every 5-7 days. I diffuse through a powerhead also, best way from my experience.
Do you use a T shape air tube splitter when use two bottles on the tank?

Someone mentioned about 3 liter coke bottle which I have never seen it before. We get 2 liter bottle here.

I have a 20G tank, so I guess one 2 liter bottle is good enough?

BTW, I tried to enter DIY CO2 as key word to search this board, but it never worked and I even tried to use the word "CO2". The search function on this board doesn't work for me. I get an error saying "IE can't display this page" after I hit the search button.
Have a look at this:

I had issues with the Hagen output in the past, and posed a similar question.
I have used the 3 liter bottles, but the 2 liter work just fine, and are interchangeable (I have several set ups).

I use 2 cups sugar, water to about the shoulder of the bottle and 1/4 tsp yeast, plus a pinch (very tiny pinch) of KH2PO4. Somewhere I read that yeast needs a few minerals.

I make larger batches:
1) Yeast + 100*F water (It does not take much to dissolve the yeast. Stir)
2) Heat water on the stove almost to boiling. (1 cup of water for each cup of sugar)
3) Put the sugar in a heat proof bowl (I have stainless steel mixing bowls) and stir in the hot water. Keep on stirring until the sugar is dissolved.
4) Add cold water, about another cup of water per cup of sugar, or a bit more. If the sugar water is still too hot wait a bit, stirring occasionally.
5) Use a funnel to fill the bottles. Top off with more cool water if needed. Add the yeast.
6) Use an intact lid to cap the bottle and shake.


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No, I don't use a T splitter for the two bottles. I just run both hoses into the "alcohol catch" bottle down into the water.... then have the one above water that will lead the CO2 into the tank.

That is pretty much it, as Diana explained.

I use a relatively high amount of yeast in mine.... this will cause it to put out more CO2 but burn out faster. I change mine every 5 days normally. If you want it to last longer, use less yeast (as Diana recommended) but you'll get lower CO2 overall.

Just depends which side you'd rather be on: more maintenance w higher CO2, or less maintenance with lower CO2. I know with my 1tsp of yeast, they're toast after 7 days. Some others I've heard use 1/8tsp or 1/4tsp and they can maintain a relatively stable output for up to 14 days.

Do make certain that you use the extra alcohol catch bottle though.
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I have DIY CO2 setup with coke bottle. Make the the hole in the cap is smaller than the actual tube so you'll have to pull the tube through the whole. No need to add any sealant.

Don't do anything fancy, just run the tube into the tank. If everything is tight, only the CO2 will go into tank.

I add 3 cups of sugar and 1/4tsp of yeast, it usually lasts me for about 3-4 weeks. First two weeks i see 1 bubble per second and then it goes down.
does this kind of unchecked CO2 production pose any threat to fish, or is the amount introduced totally inconsequential?
does this kind of unchecked CO2 production pose any threat to fish, or is the amount introduced totally inconsequential?
It's just a crutch generally, if your worried add a drop checker to monitor levels, or increase surface movement if your fishes behaviour changes to lower co2 levels.
Can I use the one gallon milk bottle for this? It's bigger and should produce more CO2 and last longer.
Can I use the one gallon milk bottle for this? It's bigger and should produce more CO2 and last longer.
The reason that drinks bottles are used is because they are designed to contain pressurised co2, a milk bottle isn't.
I know people say that you can use anything, a lot of people vouch for the big juice bottles. I just think it makes sense to use a bottle meant to contain CO2 originally. If you're doing DIY CO2 especially, then it def makes sense to not cut corners (since its so cheap already) and try to get the most out of it that you can.

To response about gassing the fish, this can happen. I know most disregard it as not being strong enough to cause any problems, but I almost killed my whole population the first time I hooked up 2 2L to my 55 gallon :tongue:

Given, that I use a higher concentration of yeast, so I get a higher production for a shorter time. With my 2 2L set up, my Cal aqua drop checker maintains a lime green color... indicating I am actually slightly above 30ppm... My plant growth shows it too. Within two weeks my plants almost doubled in size.
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Ok, I bought a 2L bottle of Sprit and try to finish it tonight. LOL.. Hopefully my glocose will not spike.

For now, I am still using a Hagen Tetafin CO2 and replaced the content. This time I added much less yeast, now I see very little bubbles coming out of it. It's not going to be enough for the tank. I see there are some algaes started to grow on the fish tank wall at buttom near substrate.

Would a 2 Liter enough for my 20G (3 cup of sugar with 1/3 tsp of yeast)?
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