TOM TM1352 Aquarium Overflow Box with Auto Start and Stop, Hosing incl. KollerCraft is highly regarded for supplying superior quality, innovative pet products and reliable service. This patented Overflow box with adjustable water flow gate provides surface skimming, removing aquarium surface contaminants. This uniquely designed overflow system allows minimum water to drain back into the sump in the event of elec trical power loss, thus preventing flooding. When the electrical power returns, automatically initiates water flow and starts the filter.