Blow-by is when the explosion in one of the cylinders of your engine gets past the rings, instead of staying contained in the cylinder.
Maybe the recipe meant to say blow-off, which is a good idea if you are using a Carboy for primary fermentation. A blow-off tube replaces the airlock, and you put the other end in a pot or bowl filled with clean water.
Wheat beers should not be racked to a clearing vessel, since they are supposed to be cloudy.
Nevada Testsite Brewery
Bottled: Belgian Dubbel, American Pale Ale, Irish Red Ale (Yeast Fuel experiment), Doppel Bock
Up Next: Brown Ale