Planted Tank Guru
Join Date: Dec 2002
Location: Portland Orygun
A few comments.
The first link has several items I will dispute. Silicone tubing is about the worst choice one can use in a CO2 system.
Soda bottles SUCK. They are unstable and hard to fill. Much better is a 2l juice bottle. Much more stable, and has a wider mouth and is easier to fill.
The picture of a soda bottle with a 16 ounce gas separator attached to it is funny. There is no way that contraption would be stable unless it was glued to the table.
Addressing both the first link and second link. The easiest and cheapest way to get a gas tight seal in a bottle cap is to simply drill a hole in the cap smaller than the OD of the tubing. Then cut the tubing at an angle and pull it though with pliers.