A filtration system for an aquarium is provided. The filtration system includes a gate chamber with a gate conduit positioned therein that transports unprocessed water from the aquarium. The gate chamber includes filtering media. The filtration system also includes a siphon chamber that is fluidly coupled to the gate chamber. There is a siphon conduit having a siphon conduit inlet at a first elevation within the siphon chamber, a siphon conduit outlet at a second elevation below the first elevation, and a crest at a third elevation above the first and second elevations. The siphon conduit empties into a catch basin, where the processed water is transported back to the aquarium.