Just so we know which filter, is this yours?
https://www.aqueon.com/products/filtration-media/quietflow-led-pro-aquarium-power-filters
The instructions for the Aqueon Quiet Flow 75 say it contains a carbon cartridge, a biological cartridge holster and a biomedia grid, and they say to wash the biological cartridge holder once a month when they say the carbon cartridge should also be changed. You mentioned a pre-filter, this is usually a sponge placed over the tube which takes water out of the tank. Is this what you have in addition to the media that came with the filter?