I ferment (well, used to) in a 6.5 gallon carboy in a temp controlled chest freezer. I use an aluminum neck handle to move it. Went to pick it up Saturday to put it in the house for a diacetyl rest and hear a glass crack and immediately saw a puddle forming. Didn't pick it up all the way and set it down. Immediately got started racking to a new carboy. Got all the beer out and went to pick it up the empty cracked carboy. It then snapped all the way - I had a giant bell-jar, with the bottom circular plate full of yeast. Turns out the entire bottom section cracked round-wise. This is the first "accident" I've ever had with a carboy. The good news - I saved five gallons and didn't create a chest freezer tub of beer (where incidentally I had 4 additional 6-gallons of wine aging). My next purchase - stainless steel fermenter.