I started my CO2 project to help the plants in my 14g grow better. I used an empty plastic 2 liter Dr Pepper bottle, 2 cups of sugar, 1/2 tsp of yeast, and water. I hooked the end of the air line tube into the intake filter to disperse the carbon dioxide.
Here are a few pictures of the project. Just click on the thumbnail.
The mixture of the lukewarm water, sugar, and yeast
I connected the air line to a gang valve (on right) to control the flow of the CO2. I then placed the bottle underneath the tank, leaving the controls near the tank for eash access.
By putting the air line into the filter intake rather than an air stone the CO2 will disperse better in the water due to the chopping action of the impeller.