# Needed: 2 Liter Bottle CO2 Recipes



## Momotaro (Feb 21, 2003)

I am going to be making a presentation to the NJAS about CO2's role in the planted aquarium. 

Part of my presentation is going to be a description of the 2 liter DIY CO2 generator. I am looking for your tried and true recipes that max out the CO2 production out of a 2 liter bottle.

Mike


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## anonapersona (Oct 19, 2002)

*Knox blocks*

I was fond of Knox Blocks -- get the Knox gelatine packets and use the recipe on the back, substitute 3 cups water with 2 cup sugar for the juice it calls for. Actually you use 1 cup at room temp t dissolve the gelatine, then boil 2 cups with the sugar and add to the gelatine in the pan then mix. Chill overnight in an 8"x8" pan, then cut into 1" cubes. I used half the pan in a 2 liter bottle, let it come to room temp and fill to 3" from the top, add 1/2 teaspoon yeast. (wine/champagne yeast worked best I think, no baking soda)

I originally tried this chilled in the bottle and the gelatine really needed chopping up to get all used up. So cubing it worked better.


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## observant_imp (Jun 30, 2004)

If you want high output and don't care about longevity, this works pretty well. It was supposed to be the Nyberg recipe, but I'd only scanned it and then waited a few weeks to try it--needless to say, it got a little mixed up. I didn't get the results I'd hoped for, but it put out about 1 bps for 8-10 days before it quit. This is my messed up version of the recipe.

1 1/3 cups sugar
splash of apple juice
1 T unsulphurated molasses 
1 T protein powder drink mix (I used soy based slimfast I found on clearance)
1 tsp baking soda
1/4 tsp yeast
warm water till the bottle starts to curve (I used RO)

When the batch runs out, pour everything off but don't wash the bottle--leave the gunk in the bottom. I go ahead and add 1/4 tsp yeast each time.

Anonaperson--what type out output and longevity do you get with your recipe?


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## ming (Dec 6, 2003)

I pour sugar up to the label
1/4 teaspoon of yeast
I let it go for about 2 weeks when it slows down, I add ~1 teaspoon of baking soda and it pumps back up to 1 bubble per 3 seconds and lasts for another 2 weeks. By the 4th week, its about 1 bubble per 8 seconds and the PH doesn't get low enough


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## anonapersona (Oct 19, 2002)

*My tests*



observant_imp said:


> Anonaperson--what type out output and longevity do you get with your recipe?


Let me pull some of the records from when I was obsessing about THAT.... 

First, I used Knox gelatine powder since is is cheaper than Jello and has no artificial flavor or color. 

Ok, my first test was 4 pkt gelatine, 2 cups water, 2 cup sugar for gelatine, chilled solid in round 2 liter juice jug. Then 1/2 cup water, 1/2 teaspoon yeast, 1/4 teaspoon sugar to get the yeast started. Then I think I filled the jug up with water, no notes here, I doubt I had only 1/2 cup of water in the jug! Didn't count bubbles, until day 10, it was so fast (guessing 50+ bpm), day 10 was 25 bpm, day 25 was 12 bpm, day 33 was 10 bpm, then I stirred the solid jell with a stick on day 38 and added tap water to get 16 bpm, fixed a leak on day 39 to get back to 10 bpm. Poured off some water and replaced on day 46 to try to get above 7 bpm, stopped on day 50 at an unstable 5 bpm. I think there was still gelatine left in the jug.

Then I started experimenting. Next was 2 1/2 cups gelatine, made with 2 cups water total, 2 pkts of gelatine, 1 cup sugar (note half the sugar as before), chilled in the bottom of jug. 5 1/2 cups liquid, 1/4 teaspoon bread yeast. Took one day to start, temp 64 that day, later days room temp was warmer. Got to 12 bpm on 3rd day, stayed at 8 to 12 bpm until day 21, then tapered to 5 bpm on day 30. I did open it and add 2 teaspoons baking soda on day 38 and a bit of salt after day 40. (note, the salt is a bad idea I later discovered) 

I experimented with using "yeast nutrient" from the brew store, it tended to make it foam, particularly with gelatine, but it was a good thing to add to sugar water mixes.

I learned that starting with hot water was a bad mistake, I would think it had cooled but I guess it still had hot spots to harm the yeast. I learned that baking soda was a necessary addition, even though my tap water is KH 9 and lots of calcium, low magnesium. I learned that wine and beer yeast did not like baking soda but bread yeast did. I suspect acid/base requirements of the different yeasts. I found that the water in the jug gets very acidic, and if you add baking soda later it will explode -- eew! stinky sticky mess!

Cutting the gelatine into cubes gives a lot more surface are for the yeast to act upon, and so will shorten the life of the mix while boosting the rate. 

My records end after a dozen tests, after that I just kept a tag on the bottle to tell me what a jug had in it and when it was replaced, so those records are lost now. I was looking for a more steady rate and not that concerned with lifespan and so I ended up reducing the sugar and cubing the mix to get a pretty stable rate that lasted 3 weeks roughly. I was using 2 cups of sugar in 4 packets of gelatine, 3 cups of water in the gelatine total. Of this pan of gealtine, I'd use 1/4, and keep the rest in the fridge -- beware, for sometimes it will mold before you get that last 1/4 used. In the bottle I'd put 1 teaspoon baking soda, 1/4 teaspoon yeast and water to 3" from the top, at that point. Near the end, I started using 1/3 of the pan of gelatine, and I think the molding of the last bit actually happened more often, so it may have been lasting much longer, sorry no notes!! 

The sugar to gelatine to water mix is important. The first test was 2 cups of sugar in 4 pkts of Knox and was too strong. At the end I was using 1/2 cups of sugar and 1 pkt of Knox per bottle, which was 1/4 of the pan of Knox blocks.


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## anonapersona (Oct 19, 2002)

*why bpm and not change in pH*

One more thing, as I was experimenting with the yeast mixes, I decided that measuring the bpm output was the only fair way to compare as I was using two different fish tanks, each with different filters and diffusion methods. 

And when I was testing, I was counting bubbles for 2 minutes with a stopwatch then averaging to bpm to be sure I wasn't fooling myself -- I found I tended to cheer the bottles on and decided I might be lying to myself, so I tried to be more scientific.


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## Wasserpest (Jun 12, 2003)

I like to keep it simple...

1 big cup o'sugar. Warm water half the bottle. Shake until sugar is gone. Add about 1/3 tsp dry yeast. Let stand a couple of minutes. Shake again. Fill up bottle and let stand for a day or two, then connect.

Contrary to Anns experience, baking soda made the mixture foam, and shortened the life of it. Yes, I used baking soda, not baking powder. My kH is around 10 so I figure additional buffer isn't needed.


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## jhoetzl (Feb 7, 2005)

I too like a jello recipe for my DIY tank...

2 packs of Non-diet, off brand Jello into an empty clean 2L soda bottle.
2 cups of boiling water and mix so that the jello fully disolves.
Swirl around carefully until the powder dissolves.
Add 2 cups of sugar and mix the solution again to disolve the sugar.
Add 2 cups of cold water and mix the solution again.
Store in the refrigerator overnight until it sets.
The next morning, dissolve/activate 1/4 TSP of bakers yeast and a pinch of baking soda in 1/2 cup of warm NOT boiling water.
Pour into bottle - do not shake or stir any further. Add about 1/8 dry yeast to the top, straight into bottle (don't know if it helps, but it seems to).
cap with a lid, drilled and manifolded using an air stone's little plastic piece siliconed into the top.
Lasts 4-5 weeks for me, at around 70F (room temp).

I use 2 - 2L bottles and the original hagen bottle in my 15 to keep the pH at 6.7ish.

The 2L bottles are started 3 weeks apart, and the hagen is replaced on an off week.


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## Gmoney (Apr 13, 2005)

I know that you asked for 2 liter bottle recipes, but I have used the 3 liter soda bottles with the following recipe:
1.5cups sugar
2 tablespoons molasses
2 tablespoons of protein powder
1.5 teaspoons baking soda
1/2 pack red star baker's yeast

Fill it partially with tank water, shake it up....fill the bottle to 3/4 full with tank water. 
This recipe has provided vigorous CO2 production for 3weeks. 
I am currently running two bottles started at two week intervals. This setup keeps my pH at 6.5 consistently. 
The CO2 is bubbled in through an airstone in a DIY gravel vac/power head reactor that turns off by timer at night.


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## fedge (Mar 4, 2004)

I use 2 cups of sugar aproximately
about 1/2 to 1 tablespoon of molases (goodies for the yeast* read to us that in tropical fish)
and then 100F water to the bell in the top... makes decent production.


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## brinks (Dec 19, 2007)

could you use corn surup instead of molasses, and what about similac baby formula for the protein powder (has lots of good stuff in it) and could you use a small bit of a plant spike like jobes?


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## daverockssocks (Dec 1, 2008)

I guess I use the simple setup. 

3/4 cup sugar mixed in 2 cups of hot water and dissolved to create a saturated liquid. Add to 2 liter bottle then top off with cool water (will reduce the heat present in the hot water) and then add 1 teaspoon bread yeast. 

I get solid production for about 18 days with production starting in earnest 1 hour after the mixture is hooked up.


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## notoptimal (Jan 5, 2007)

I've been using this recipe for some time with good success:

2 cups sugar
1 tbsp blackstrap molasses
1 boullion cube (I use beef)
6 cups hot tap water
1-2 drops dechlorinator
1/8 tsp baking soda
1/8 tsp epsom salt
1/8 tsp dry active yeast

I put everything but the yeast in the bottle, cap it and shake until most of the sugar is dissolved (the boullion cube won't dissolve immediately). I then add the yeast, leave it floating on top of the mix, and reconnect the bottle to the system. I'll change the bottle out after 2 weeks (I run two bottles), but have gone up to about 3 1/2 weeks without changing a bottle before it becomes a problem. You could probably get away without the epsom salt if you wanted.

I keep my bottles in a bucket of water with a small submersible heater maintaining about 85°F. This keeps the temperature (and CO2 output) constant. The water bucket also provides a good measure of remaining bottle life -- when the bottle starts to float, you're about midway through the bottle's useful lifetime (give or take).

notopt


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## macclellan (Dec 22, 2006)

This thread is four years old. I think it's safe to say that Mike gave the presentation already.


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## ivan.f (Aug 12, 2011)

Still pretty useful


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