I have only done this outside but it probably works good inside too. The advantages are, no pump, can use dirty water, very low tech, can work for a long time unattended.
Best vid for understanding it is http://www.youtube.com/watch?feature=player_embedded&v=3yQOVUR1TpQ
Image may be NSFW.
Clik here to view.
Playlist is at http://www.youtube.com/playlist?list=PLkzXlmAwZTZdjGtjJpCYm2gSGVGwA033M&feature=view_all
Brian
