Efficient Co2 Mix

1 teaspoon of yeast with 1 tablespoon of sugar in 1 litre of water

what size is the tank?

I just replaced my mix after 3-4 weeks.. And heres what i use
(this is for a 10g tank)
One 2L bottle:
1.5 cups of sugar
1/4 teaspooon of yeast
1 teaspoon of baking soda
5-6 cups of warm water

I do use another 1.5L bottle and cut the ingredients by around 1/4..

The key here is to hydrate the yeast before you add it all to the bottle.
So do this first:
Add the sugar to the bottle and fill it with the 5-6 cups of water (warm not hot or cold), then cap it and shake shake shake until all sugar is dissolved. Then take a shot glass and fill it with the water/sugar mix. To the shot glass add the 1/4 teaspoon of yeast and leave it alone for 10min, come back after 10min and mix it and leave for 5 more minutes. After the 5 min pour the yeast back into the bottle and mix again a bit. Add one teaspoon of baking soda and shake again. For now you dont have to add it to the tank right away. You can let it stand capped for 12-24hrs. The next day take the bottle and hook it up to your tank. Bam you are done. Mix should last you 3-4 weeks. And weekly you can just swirl the bottle

i like bk's stuff about how to mix, however i would suggest instead of using one 2l bottle use 2 x 1l bottle

on one of my tanks i use three 1l bottles and refresh each bottle once per week, one on a tuesday, one on a thursday and one on a saturday.

the reason for doing this is to keep the co2 levels constant as the downside of diy systems is the inconsistent co2 levels which can actually encourage the growth of algae

replacing weekly kinda defeats the purpose of a diy, since its supposed to be affordable and easy. But I guess what ever works for one, he should keep it up.