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 Continuous Siphon Overflows/Prefilters are the best means for
getting water from an aquarium to a filter system without expensive
modifications to the tank. They quietly skim up to six times more water
than units with tubes.
The advantages of CPR Continuous Siphon Overflows/Prefilters include:
* Adjustable water level allows you to easily change the level in your tank. * Black top reduces algae growth. * Plastic screen to prevent fish loss. * Quiet operation.