I'm working on my DIY CO2 set-up while I wait for my aquarium and such to arrive. I'm not using plastic bottles. I'm using glass. Right now I'm waiting for some silicon to set on one try using a colored glass wine bottle and a pour spout. If that doesn't work I'll use a glass juice bottle. I'll be able to drill the lid like the plastic soda bottles are done. I'm having the air tube go into a glass Spice Islands jar as a DIY bubble counter. I've already drilled one hole in the lid and inserted and sealed in the "out" air tube. I also installed the check valve after the bubble counter. Friday I'll test the wine bottle for air-tightness with a water/sugar/yeast mix. If it's tight and works well, I'll drill the second hole in the bubble counter lid and seal it in. I'll give it a few days to set up then try the whole system. If all goes well, by the time I get my shipments, I'll be ready to get plants. When I'm ready to start using the CO2, I'm going to try the jello method. I'll just have to cut the amounts of everything to fit in my wine bottle.
"Aquarists are a brave lot. We mix water and electricity every day."