Recently I have been getting relatively low attenuation during my fermentations. I've run into the problem with White Labs London, British, and California yeasts. I aerate well, start out at the right temperature and ferment at the right temperature, but still get poor results. I am concerned that it might have something to do with the size of the carboy and the blow off tube I am using. For the primary fermentation, I typically put my cooled wort into a 5g carboy, but when the fermentation really starts going off I lose a lot of Krausen out of the tube. Since ale yeast is top fermenting, could I be losing a lot of yeast out of my blow off tube that could negatively affect my fermentation? Should I use a 6g carboy instead for the primary?
Any thoughts are appreciated! Thanks.