If you go w/ yeast, I can tell you a couple of things...
1) Don't use more than ~23% sugar (by vol.) as it won't get used. A 23% sugar/72% water mixture gets up to 10% ethanol at the time the sugar runs out. Much more sugar than that just goes to waste.
2) run the CO2 tube right into the inlet basket of the Eheim. Working well for my 2215.
3) To keep some air in the mix in my 5g, I have an air pump on a timer, stone nr. top edge of water. It runs 15 min. on, 60 off, repeat.