Addie -- I've been doing some reading and research... so I am sort of familiar with the bog thingie. Am I correct in thinking that you use the little basin of bog plants as the filter, rather than a purchased filter? You use a good pump to move the water through the bog and out to a waterfall or little spillway? Is it then just maintained by mother nature? Do you have anything you have to change and clean in the bog filter? Thanks!