I have work to do on the diffuser system, but this is a good start and I can see if it works. I used three 2-liter bottles. Two have the yeast sugar combination and the third ensures no muck from the solution gets to the tank. The air flow from the third bottle goes through a backflow preventer . This way, if water ever sucks back up the hose, it will it will be stopped from flooding anything. The hoses from the solution bottles are submerged in the third bottle. When the system starts generating CO2, I'll be able to get a bubbles per minute count.
Theoretically, in this lightly stocked tank, the plants don't get enough CO2 to make use of available light. Guess we'll see what happens, especially once the diffuser is improved.