I have just upgraded from a 75g tank to a 125g. I have a FX6 filter that was running on the 75g that was moved to the 125g. My main question is can I do a sump for the major debris removal and then use the fx6 for fine filtering and to return the water back into the tank? The tank is not drilled so would need to do a overflow box of some sort, also seeing it is a RES tank (with a large pleco and Jack Dempsey) I only have it filled to about 65-70%... I was thinking a sump between 20 - 40 gals to be able to keep up with the flow that the fx6 will pull... Any thoughts or ideas? I also thought about putting a second fx4/fx6 inline with my current fx6 and just fill with poly fill as a debris collector to keep the main fx6 from getting all gunked up...