konrad, I think he probably added the baking soda because several websites have recipes which contain it. They state it helps keep the mixture less acidic. Don't know... I'm new to CO2 myself and I did not use baking soda.
Sean, my CO2 experience just started a week ago. I can tell you that mine bubbles only periodically. I have on of the power head/gravel vac reactors. I have two 3-liter bottles on my system. Only periodically do I actually see bubbles rising from my airstone in the reactor. However, in my case, this is not an issue because of the reactor design. When the CO2 is bubbling, it rises to the top of the gravel vac, where it is trapped and subsequently pummelled by the water stream from the power head. The trapped pocket of CO2 grows and shrinks depending on how much CO2 comes out of the system for a given period of time.
Definitely follow konrad's advice on checking for leaks. I had a devil of a time getting my sytem all sealed. Finding something that will seal the poly-ethylene cap of the typical soda bottle is a PAIN!!! I thought I had it sealed but my system would not generate any CO2. I finally squeezed both bottles to put pressure on the system and heard one of the caps hissing. I filled a plastic tub with water, immersed both bottles and had bubbles all over the place. Tried several methods of sealing before I finally got it done.
Hope some of this helps you with your problem.
