DIY CO2 Setup Only Works Well Sometimes - The Planted Tank Forum
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post #1 of 8 (permalink) Old 08-16-2015, 02:37 AM Thread Starter
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DIY CO2 Setup Only Works Well Sometimes

I want to ask people to help me solve a mystery. Basically, I'm wondering why do CO2 yeast reactors only seem to work optimally occasionally (that is, to produce a lot of CO2 for up to 2 months at a good strong stream), but most often other times, they are very weak, have a very low stream of CO2 bubbles, and stop working within a couple weeks.

I once wondered if it mattered if the water in the soda bottle was filtered or spring water or not (tap water with the usual city added chlorine), or if the active dry yeast should be a brand with or without the preservative added (sorbitan monostearate) but that does not seem to be the issue.

Has anyone else had this problem? Some rare times when I set it up, the output is robust and works well ... but often I find it won't work at first using the small pinch of active dry yeast recommended in the do-it-yourself procedures, and I end up adding a bunch more yeast a day or two later after setup. Sometimes I have two 2-liter bottles connected to each other, sometimes just one. When I first tried doing a DIY setup, I used one of those glass J-shaped diffuses and it worked OK, but only once. Ever since then, those diffuses have never worked (there was never enough CO2 gas pressure to produce the stream of lots of tiny bubbles) and I had to use a standard airstone. Oh, and I do add a pinch of baking soda to the sugar+active dry yeast+water mix.

My point is that often some factor I don't know about causes the setup to be a big dud. It just doesn't work... and a few times, it does.

Here is a photo of my setup:

Last edited by NavyDogFish; 08-16-2015 at 11:36 AM. Reason: Mentioned baking soda.
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post #2 of 8 (permalink) Old 08-16-2015, 02:08 PM
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Do It Yourself co2 is hard to regulate and be consistent because you are depending on organisms to convert sugars into co2. That means your rate of co2 into the tank can vary based on how fast the organisms can convert. You say you use a pinch of yeast that could be your issue with slow co2 amounts. Also maybe you don't have quite enough sugar added to your mix. If the yeast does not have a lot to eat it will not put off a lot of co2.

Some diffusers also do not like to work well with do-it-yourself systems. Don't use air stones in place of them they will only get brittle and break and put off too large of bubbles.

Is that the complete system you use? You should have a second bottle as a drop counter /filter in between your yeast bottle and your diffuser.

Here are some pics of my system. I also use a check valve in the line closer to the diffuser. Sorry the pics aren't that great. Those are tiny tiny tiny bubbles coming out of the diffuser. They take about 5 seconds to reach the top of the tank.
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Last edited by goatnad; 08-16-2015 at 02:39 PM. Reason: added pictures
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post #3 of 8 (permalink) Old 08-16-2015, 03:14 PM
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It is the way you are re-constituting the yeast. First put 1/2 cup of lukewarm water in a small bowl or soup mug. Not warm enough for a bath but warmer than room temp. Add 1 teaspoon of sugar and whisk it with a fork for 30 seconds. This adds some o2 to the water and mixes the sugar. Now add 1/2 teaspoon of REGULAR yeast, not the rapid rise yeast. When adding this yeast you must shake it slowly into the water while whisking with the fork. If you just dump it in it will clump together and most of it will die. You want the yeast to just sprinkle onto the water surface and be whisked in continuously. Once the yeast is mixed in completely then let it sit in the cup or bowl for 10 minutes, whisking once in a while.

While the yeast is sitting add 2 cups of sugar and 1 teaspoon of baking soda to your 2 liter bottle. Fill it with room temperature water up to the top of the label. Not cold and not hot, Room temperature. After your yeast has been whisked again at the end of the 10 minute period add it in but do not shake it. Just let it settle on it's own and hook it back up to your tank.

It is best to have 2 bottles and change one per week. That way there is always a fresh bottle since it takes a day for a bottle to settle down to steady production.
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post #4 of 8 (permalink) Old 08-20-2015, 04:04 AM Thread Starter
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key, when you mention water do you mean tap water or should it be filtered or spring water? (And if you say warm should I heat it on the stove?) And goat, how exactly does your particular 2 bottle setup work and how does it go together? (What are all the components and how do you set them up?)
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post #5 of 8 (permalink) Old 08-23-2015, 02:59 AM
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why you won't using baking soda + citric acid reactor? It's easy, cheap and much more stable and predictable in comparison with any kind of bio-reactors.
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post #6 of 8 (permalink) Old 08-23-2015, 04:20 AM
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The DIY link in my sig may offer some food for thought

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post #7 of 8 (permalink) Old 08-23-2015, 05:05 PM
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I can only offer a reliable recipe.

1 - 3 liter bottle half full of 90 degree water.
Add 2 cups sugar and dissolve completely.
Add 1 teaspoon of baking soda and dissolve completely.

Mix 1/2 cup 95 degree water with 1 teaspoon of dry yeast and dissolve completely.
Pour this into 3 liter bottle and shake well.

When this mixture can no longer pass bubbles through a check valve,
don't throw it away.
CO2 has stopped because of alcohol content and dead yeast.
There is still available sugar.
Add 90 degree water to existing mix say 85-90% full.
Mix another 1/2 cup 95 degree water with 1 teaspoon of dry yeast and dissolve completely.
Pour this into 3 liter bottle and shake well.
2nd application of yeast will almost last as long as first.

Do you use that bubble counter/atomizer?
What pressure does it need to operate well?

Air stone hooked to CO2 bottle, where does this get placed?

Suggested recipe is used with a reactor tied to canister filter output.
It can easily provide 60ppm in my 40 gallon.
I also have nothing breaking the surface to release CO2.
All return water to tank enters below the surface.
When CO2 gets too high air stone may be needed.

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Growing is not that difficult.
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post #8 of 8 (permalink) Old 08-23-2015, 10:02 PM
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Yeast is also temperature dependent. In the winter, you're not going to get the same output as the summer.
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carbon dioxide, carbondioxide, co2, diy, generator

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