Case and point. I have an Allglass Aquarium with 1 overflow.I have a 9.5 Mag Drive on mine and its to much. I only have about 2.5 feet from the sump to the DT. I had to direct some of the flow back to my return section in my sump. I would suggest you figure out your head pressure and then look at something smaller. You can get the rest of your flow from PHs.