I've always heard that you need a glass carboy to ferment in, though the plastic one are far cheaper and easier to get. It occurs to me that a two stage fermenter like myself typically uses a plastic bucket type fermenter for the primary. That works fine, so why is it bad to use plastic for secondary? The plastic used in modern plastic carboys is obviously not the same as what is used in my food grade plastic bucket, but if it's safe for drinking water, why not beer? Anyone with actual experience?