I have a 6.5 Gallon that I use for primary fermentation, and a 5 gallon that has served me well for secondary fermentation. However, for the next batch that I'm planning, I was going to add a few pounds of blackberries to the beer in the secondary fermenter. Will this cause a problem in a 5 gallon carboy? Do I need to purchase an additional 6.5 gallon in order to create enough space for the fruit?