It is overkill but also allows for longer periods between cleanings, also there is no such thing as to much filtration. I had a FX4 on a 75 and run a FX4 & FX6 on a 150 so I may have a bit of bias. I clean mine every other week or so but I have about 37 fish in the tank.Lol!!! Just showed hubby this thread and now he’s asking if we should get the FX6? Overkill, right for 90 gallons? I think he’s hinting that if we overfilter then we can go two weeks between water changes. I don’t think it works like that, does it? Like Old mentioned, the fish need the replenishing of minerals etc.