Scodiddy, I use a Reeflo Blowhole 1450 pump for return which theoretically gives me 1400gph at max setting. Since the pump has to raise the water up by about 5 feet to the display tank and I also divert some of the return water to GFO, carbon, calcium, and UV reactors, I would say the flow thru the DT is about 700gph. Keep in mind I have two MP40s and recently added a WP25 for water movement in my tank.