A water inlet system for an aquarium is disclosed along with a siphon stopper and a method of attaching the system to an aquarium. The water inlet system is designed to pass through an aperture formed in a sidewall of the aquarium. A tubular member is connected to a pump which can supply water from a reservoir to the aquarium. The tubular member passes through the aperture and into the aquarium. An adapter having a spout is connected to one end of the tubular member. In addition, a siphon stopper is secured to the adapter, above the spout, and serves to break any back siphon that may develop should the water line in the aquarium drop below a predetermined point. The method includes the steps of attaching the water inlet system to the aquarium.
