Join Date: Sep 2003
Location: San Francisco, CA
I ran a tank filterless for almost two months for very much the same reasons as you, EvilKen. Something about the simple elegance of plants and fish living symbiotically in a simple and hands-free tank appealled to me.
For the two months that I did have the tank running "Amish" (i.e. with as little technology as possible), I was quite pleased with it. The plants grew, albeit slowly, and the fish did well enough.
Then on a whim—also known as "impulse shopping"—I picked up a filter and slapped it on the tank. Plant growth exploded! In one week, plants grew at a rate that would have taken four or five times as long had the tank not had a filter.
Besides the slow growth, and assuming you are careful in the types of plants and fish you pick for your tank, I—and this is just me talking from experience and not from science or research—I don't think you'll have too many problems. Why not give it a shot? You only live once, right?