I do not believe a filter is necessary (although I may be wrong). I did a "fish in" cycle (or at least what I assumed was a fish in cycle) with Eponine last summer. It followed the same "cycle" as mentioned in the cycling sticky when I tested and changed the water.
I know that I have heard that using gravel from a cycled tank is just as effective as filters from a cycled tank. So, I would assume the bacteria lives in the gravel. I know it lives on the plants and decorations and such. I knew the water did not have much in it, but I have heard of people using water from cycled tanks to kick start their cycling process. So, that's what I wasn't sure about.
At PetSmart (where I work) we tell people to cycle tanks that don't have filters. We tell them to do the same thing as the fishless cylces listed in the sticky say. Those who do have filters, they tell to run it for about a week with the filter running. Not, that I'm saying these are right.