DIY CO2 Question

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Aquarium Advice Regular
Jun 13, 2003
Flint, MI
Last week I decided to make my own CO2 system for my 10gal tank. I used the standard method, 1 cup sugar, 1 teaspoon yeast, 1 teaspoon baking soda, filled with water to 3 inches from top. It worked great, I was getting 3 bubbles every 8 seconds after 2 hours of setup. It got even better after that, 10 bubbles every 2 seconds. That lasted for about 4 days and my plants flourished. Then it really slowed down, 2 bubbles every 20 seconds. Then the yeast, sugar, and baking soda seemed to clump together and sink to the bottom. I shook the 2 liter to get everything mixed up but after an hour it all sunk to the bottom again. Now it is the 7th day and I get 1 bubble every 1m30s. I am using a regular airstone as a diffuser. What could be going wrong?
I use 2 cups sugar with a 2 liter bottle, lasts much longer. I get about 17 days of good bubbles out of that.

How did you attach the tubing to the bottle cap? Check that for leaks.

My best guess is that it used up all the sugar. The clumping/sinking is normal.

What kind of filter do you have on the tank? If possble, run the co2 tube right into the filter intake. it smashes up the bubbles and you get better adsorption of co2 ito your water.

If that is not an option, I'd get the Hagen co2 diffuser (around 10 bucks I believe). you don't have to purchase the whole system, just the co2-proof tubing, and the diffuser (essentially a bubble ramp, the bubbles have a long time under water, and the co2 gets adsorbed.)

Either of these methods is way better than a standard airstone, which is very inefficient.
yes, more sugar, less yeast

I use 2 cups sugar, 4 cups water, 1/2 tsp yeast, no soda in a 2 liter bottle.

you can try as little as 1/4 tsp yeast - it will take a few days to get "started" but will last almost a month, fairly even production curve.

most yeast = faster production = more gas

more sugar = longer production

so why not use a LOT of yeast? well, the yeast slowly poisons itself as it eats the sugar. the more yeast, the more poison. at a point, it won't mater how much sugar you use, the yeast will not be able to eat it all before poisoning themselves.
There definitely is not a leak, the airline is connected to the bottle through a rubber cork.

I have an aquaclear mini filter. Should I put the airstone in the intake section or not use an airstone at all and just put the tube in the intake area?

I will try adding more sugar and less yeast to my mixture when I mix up a new batch. It sounds like the best way to get good results is to use trial and error.

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