This is a good link to the instructions:
http://www.plantedtank.net/articles/DIY-Yeast-CO2/7/
Instead of using a drill to make the hole in the tops, you can heat up a screw driver with a lighter and then force it through. Thats what I do sometimes, when I don't feel like messing with the drill. Then you can pull the airline through with pliers. I like to cut the end of the airline at an angle...makes it easier to grab and pull with the pliers.
In all you need the 2 2L bottles. I like to use juice bottles because they are flat on the bottom...makes them sturdier. You will want to make the holes in the tops (1 in each top) and then pull the airline through as described above about 3/4" to an inch into the bottle. Usually I don't need to use silicon around the hole, but if it leaks, you may need to. Make sure you put a check valve between the bottles and the diffusor. I use a T-splitter to connect my 2 bottles and then a short piece of tubing, then the check valve. You don't want to chance the yeast mixture getting into the tank...or water filling up the bottles.
You'll need some type of diffusion method. Inserting the tubing into your filter will work, but it can be noisy. Another method is using a limewood airstone, which makes tiny bubbles, and placing it under the intake of the filter, so that the bubbles going into the filter are smaller (cuts down on the noise a little). I use powerheads to diffuse my CO2, and its noisy like a filter would be because it goes directly into the PH.
You'll want to find a recipe that works for you, but I'll share mine. I use 1 1/2 to 2 cups of sugar (doesn't make a difference IME, if I'm running low, I'll only use 1.5c) and 1/4 tsp of yeast. I put hot water in the bottle, about 1/3 full, then I add my sugar and shake like mad to dissolve it. Then I add lukewarm water until its about 3-4 inches below the top of the bottle. Then I add my yeast and shake gently. Then I'm ready to go. You will usually see bubbles about 12-24 hours after mixing it up (or atleast I do
).
Nothing to it.
I thought at first it would be hard to do, but really its just time consuming (especially if you have 2 bottles on each of your 3 tanks...gets old after awhile). It works great though, if you can't go pressurized.
Hopefully my instructions are easy to understand, along with the ones from the website.
If you can find some polyurethane tubing (not at a lfs), that is best to use. Regular clear airline will crack eventually and silicon loses alot of CO2, but if you only have those 2 to choose from, go with the silicon.
