Thanks for that response. So let me get this correct, in the first bottle, put a cup of sugar and teaspoon of yeast. How much water should I put? What goes in the next bottle exactly..? The tank will be about 78°F .
Also, I know I need something to put it into the tank from the tubes correct ? Should I get a diffuser?
Fill the sugar and yeast bottle about 80% full of water (sugar already dissolved). The tube coming out of the first bottle should extend below the cap only about 1/4".
The second bottle should be filled about half to 2/3 with water only. It is a trap incase the yeast bubbles up into tubing. You can also use it to count the bubble rate.
The tube coming into the second bottle (from the yeast bottle) should go to the bottom. The CO2 coming into the second bottle bubbles up through the water. The tube coming out of the second bottle should extend below the cap only about 1/4".
IMO, a http://www.amazon.com/gp/product/B0002DI1W4?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 is the best way to introduce DIY CO2 into the tank. It extends the time that a CO2 bubble is in contact with the aquarium water. For some reason they take a few days to settle in and work properly. I suspect that either the plastic needs to absorb water, or a film of bacteria (stuff that turns ammonia into nitrates) needs to grow on the surface. Bubbles don't move up the ladder properly when it is first put in. It has something to do with the surface tension on the bubble and its contact with the plastic.
You know it is working well when the bubbles get smaller and almost disappear as they get to the top. It is kind of enjoyable to watch the bubbles travel up the ladder.
Ceramic disk diffusers (often glass) usually require more pressure than DIY CO2 produces.
The tank temp doesn't matter. What matters is the temp of the yeast mixture. The warmer it is the more CO2 it will produce. If you work out a way to warm the first bottle, you can adjust the temp to control the flow rate.
As you renew the sugar/yeast mixture you can experiment with the amount of sugar. Adding more sugar will give the yeast more food and extend the life of the mixture up to the point where alcohol poisoning is what ends it. Adding more sugar beyond that point just wastes sugar. So, you could experiment with cutting back or sugar or adding sugar until you find the point where more sugar does not increase the mixtures effective life.