CPR Aquatics CS100 Siphon Overflow 800 GPH. Works on 10 to 65 gallon aquariums. A built-in overflow is the most efficient method of draining aquarium water to a filter. If your aquarium does not have built-in overflow, CPR Aquatics Siphon Overflow are the best means for getting water from an aquarium to a filter system without expensive modifications to the tank...