That is a concern of mine too.. but this statement makes it sound very adjustable!
The VorTech uses the most advanced motor technology available, allowing the water flow rate to be completely controllable. Operating on tanks between 20 and 500 gallons and producing between 100 and 3,000 gallons per hour of flow, the VorTech is the most versatile flow product on the market. The VorTech is designed to operate on gap thickness from 1/8" to 3/4".