I have a 5 gallon glass carboy that I use for a secondary when making 5 gallon batches. I would love to get two batches of beer going at a time and I have a 6 gallon carboy that I've used for wine. ...
I use plastic PET carboys ("Better Bottle" brand) for fermentation, mainly because they're cheaper, lighter, and safer. I use only chemicals to clean them (no brushes), so I'm not too worried about ...