I have a 180 gallon tank with an fx6. I don't know if the fx6 not having a strong intake but I have alot of fish waste on the bottom of my tank. I do clean my tank every 2 weeks and I notice my fx6 is not really that dirty when I clean that too. My old 406 with my 80 gallon tank. That 406 was full of waste when I do the daily 2 weeks cleaning and cycling.