Abstract: The present invention is an intermittent cycled biological filter. Liquid enters a filtration container through an inlet line and travels to the bottom of an internal cavity of the container, passing through any filtration media in the container. The liquid then exits through a siphon mechanism having external and internal siphon tubes connected to an internal cavity of the container. The liquid travels up external siphon tube, down internal siphon tube, and through an outlet line. A siphon break tube connected to the external siphon tube destroys the suction pulling the liquid up once the liquid level in the container drops below a certain level, allowing liquid to begin filling the container again. This allows intermittent wetting of the filtration media. In certain embodiments, multiple filtration containers may be connected in series and/or parallel to allow for a greater volume or level of filtration.