A system and method are disclosed for filtering liquid using a filter platform that is not rigidly affixed to a container containing the liquid to be filtered. The platform may be buoyant so that as liquid flows from one side of the platform, through a filter, and then to the other side of the platform, the platform may move, thus reducing the volume of a container or portion of a container that holds the unfiltered liquid. Alternatively, the platform may be heavier than the liquid to be filtered, may be either set in place on a support structure or else set on top of unfiltered liquid and allowed to sink downward as liquid is filtered. The system may further comprise a flexible membrane that allows two sections of liquid to be separated, even while the platform is moveable.