Well, let's see. My CO2 experimentation on one tank was an instant success. The other tank, the diy bottle was too close to a heating duct, so the temp fluctuated and the yeast went crazy, overflowed the bottle into the tank. Then, I unplugged the tube from the stop valve and left the one end of the tubing hanging out of the tank. Water slowly siphoned out through the airstone, up the tube and onto the floor. Yeah, stupid, I know. As for the bottle, the other end of the line clogged up in the stop valve and pressure built up in the bottle. By the time I got around to taking care of the bottle, it was pressurized beyond capacity, and when my stepdaughter picked up the bottle, the stop valve came loose and hit the wall rather forcefully... only inches from my head. Yeah... very stupid, I know.
If you do diy, make sure there is a stop valve (to keep water from backing up into the bottle) on the line. A lot of people also have a second bottle on the line so that any liquid that gets into the line doesn't go into the tank. Make sure the diy bottle is in a secure place where it won't get knocked over.
Get KH and pH test kits to make sure that you don't have too much co2 going into the tank.