Originally Posted by BeerCigars
Can blowoff be prevented if you use a larger carboy, say 6 gallon instead of 5?
With a 6 gallon carboy, and warm temperatures, you're probably going to have to use a blow-off tube for a 5 gallon batch. If you use a 6.5 gallon carboy, you probably have less of a likelihood of needed a blow off tube. Wheat beers and warm temperatures tend to cause more krausen and more vigorous activity, so they more often need a blow-off tube.
I use 7.5 gallon buckets for 5 gallon batches, and never need a blow off tube. I needed one about two years ago, when a fermentation got too warm. That's the only one I ever used, though.