That's pretty cool. I think I'd use a powerhead and make it easier and with more flow. I'd like to have the thing out side of the tank too where water can be sucked out of the tank through a small intake with a cylindrical sponge filter attatched to keep the bigger particulates out.

Then the water would be drawn through media condusive to biological filtration, and some carbon too, and then have it run back into the tank through the submersed powerhead with air venturi.