Apparatus and method for removing foreign matter from water at selected levels in an aquarium utilize a valving mechanism placed between a skimmer adjacent the upper surface of the water and a lower inlet adjacent the lower bottom of the aquarium, the valving mechanism being operated selectively to control the relative volume of the flow of water through the skimmer and through the lower inlet, and a corresponding continuous withdrawal of water, together with entrained foreign matter, passed through either one or both the skimmer and the lower inlet so as to remove foreign matter from selected levels in the aquarium.