Originally Posted by BigJim
Pick an overflow box that's rated for more flow than your pump is capable of producing. That way your pump flow rate will be the controlling factor in the loop. If your overflow box can't keep up with the pump, the display tank will overflow. If the pump can't keep up with the overflow box, nothing bad happens.
be careful doing this,the pump needs to be rated just below the overflow rate or the flow may not force the bubbles through the syphon.