I come to the aquarium hobby with a few other hobbies, one being wine making, and the other in electronics. For this reason, I wanted to post my take on a DIY CO2 system. I'll report back on how it works out, once I have it set up. But for now, things will have to wait for a few days until I get my new lighting fixture and my plants.
Here's an image of all the parts needed for this. Sorry for the picture quality.
The first thing I noticed about a lot of DIY CO2 systems is that a lot of people were using old juice or soda plastic bottles. All fine and good if your tank has a dedicated stand where you can hide your CO2 system. I don't have room for all that, so for this reason, I wanted to make a CO2 system that's more appealing to the eye, while working more efficiently, and hopefully with less leaks than you'd get with hot gluing a tube into a plastic bottle lid.
For this reason, I went with a dark 750 ml wine bottle. The dark glass will hide the ugly amber color of the yeast, and hopefully provide better protection against CO2 explosions.
The problem, of course, is to get a small tube to work inside a larger bottle opening. One option is to use a cork. Synthetic (rubber like) corks are available for cheap from home brew wine suppliers. You can drill a hole in the cork, and place the tubing inside, but I'm betting you'd get leaks using this method. Plus, removing the cork to change out your yeast formula would quickly become an irritation.
For this reason, I opted to go with using a liquor pourer (sometimes called a wine pourer). These are available from bartender supply houses online if you have trouble locating one. The one I have is plastic, but here is an image of a metal and rubber wine pourer.
This results in a very snug fit over the wine bottle, and it's designed to prevent spills. It should be air tight enough for CO2 generation.
The next problem is that the check value does not fit snugly on the top of the wine pourer.
For this reason I picked up some heat shrink tubing at Radio Shack for 4 bucks.
Heat shrink tubing comes in all colors, but it's most commonly found in black, and is used in electronics to prevent unwanted electrical connections. I chose clear tubing here for demonstration purposes.
Using a pair of scissors to cut the tubing to length of the intake part of the check valve,
I put the tubing on the check valve and *quickly* ran a lighter over the tubing. The tubing shrinks and form fits around the check value.
Now the check valve and the liquor pour fits together snug.
From there I just run the tubing from the check value to the CO2 diffuser.