AFAIK Fat Tire isn't bottle conditioned, its filtered, force carbed, and bottled.
so, you'll harvest nothing.
even bottle conditioned beers...many of them have a different yeast added to prime the bottles, different from the primary yeast for fermentation.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10