Low nitrates,,,More water volume in your setup,,,More stable bio system,,,less or no more unwanted algae in your main tank because you are providing a perfect enviroment for it to grow in the ref,,,No more Ph swings(if you keep the ref's lights on 24/7)..A safe haven for macro organisms like pods and bristle worms to grow,,,That's just a few...Oh,and a much better enviroment for your fish...