A method of affixing an overflow system to an aquarium is disclosed. The aquarium has a bottom, at least one sidewall, an open top surrounded by a top edge, and a frame having a bottom edge. The method includes positioning an overflow device in the aquarium. The overflow device has a front wall, a back wall, a first sidewall and a second sidewall all secured to a bottom wall and extending upward therefrom to create a chamber having an open top. The front wall, the back wall, and the first and second sidewalls all have a plurality of slots formed therethrough which are configured to receive water from the aquarium into the chamber, and the bottom wall has an enlarged aperture formed therethrough. A first aperture is formed through the sidewall of the aquarium and an attachment mechanism is used to attach the enlarged aperture to the first aperture.