Step 1: Materials
A one liter gatorade bottle (or similar)
Several feet of airline tubing (vinyl is ok, but silicon is better)
An air diffuser
A suction cup to fit your tubing
A check valve
Aquarium grade silicon
A planted tank (duh?)
Step 2: STEP ONE
Step 3: STEP TWO
Step 4: STEP THREE
Step 5: STEP FOUR
About 6-10 inches away from the cap, cut the line in half, and plumb in your check valve.
MAKE SURE that the arrow is pointing AWAY from the bottle cap, otherwise you will have a ticking yeast bomb sitting under your aquarium.
The picture is of the finished project. Just pretend you don't see that part though ; )
Step 6: STEP FIVE
You want to let this dry for 48 hours before using the setup.
Step 7: STEP SIX
I don't think I need to explain how to put on a bottle cap. I'll give you guys some credit.
Step 8: STEP SEVEN
Step 9: STEP EIGHT
Step 10: STEP NINE
Step 11: STEP TEN
I don't have any pictures of this, but its just like following a recipe.
First, you fill your bottle half way up with pretty warm water. You don't want it too hot, but not too cool.
Now you want to add 1of cup sugar.
You will need an extra cap that fits the bottle. You want to shake the hell out of it until you can dissolve as much sugar into the bottle that you can.
Fill the bottle up to about 2 inches away from the top with COLD water. Put on the other cap, and shake it some more. You want the water to be a little warm. Too hot, and it will kill your culture.
Now add teaspoon of bakers yeast, and just a pinch of baking soda. Give it a gentle shake.
Take your contraption to your tank, and screw on the cap with the hose, and let it sit. It might take up to 3 days to start bubbling, but soon, the yeast will metabolize the sugar, and produce CO2. The more sugar you add, the longer it will produce CO2. The more yeast you add, the faster CO2 will be produced, but it will deplete pretty fast. The baking soda is to keep it steady.
Every three days, give the bottle a gentle slosh around to mix it a bit.
Step 12: STEP ELEVEN
At night, when your lights are off, run an airstone to prevent pH swings.