I use pure O2 for aeration, so I never used a filter.
Using an airpump, I'd be a little more wary, but I'd make my own filter with some aquarium filter floss or quilt batting and a plastic tube with flared ends.
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