I will be about 2 cups sugar 1 1 / 2 liters of water, 1 / 4 teaspoon of yeast an a little baking soda. The problem with DIY's PH value is a bit shaky off as carbon dioxide production, a new batch from the initial value so that your PH on the increase or decrease based on the amount of carbon dioxide will enter the tank. I found many recommend the use of 2 liter soda bottles, but I'm currently using 2 1-gallon jug of water plants, 33 gram cylinder.