LOL thank you!!
I attached two pics although the second one is totally indistinguishable from a black blob. My phone was just not cooperating to take a picture of the intake through the blue water (I'm medicating with methylene blue this is my hospital tank)
The first one has the inside of my aqueon. I actually meant to keep in the wavy blue cartridge holder but I forgot to put it in and then I stuck in bio balls and it didn't seem worth the bother to dig them back out.
Mostly I wanted to show you how I just shoved in polyfill pretty much wherever.
You just don't want to stuff it so tight that it restricts the flow. I just put a little bit i the left part of the filter so I didn't mess with the flow. To be honest I just eyeballed the amount. Looked at how it flowed with and without, saw no difference, called it good. Was just trying to fill in any empty space with some sort of filter media.
I haven't had this tank/filter running for long but I can tell you when it DOES get gunk, it's ALL on the prefilter sponge and not inside the filter, which is awesome.
Your idea about the green scrubbies is perfect!
The prefilter sponge I have on there is for a Fluval Edge and it fits perfectly.
It is specifically this sponge:
Amazon.com: Fluval EDGE Pre-Filter Sponge: Pet Supplies
So if you need anything else from amazon to get it as an add-on, cheap!
Or this
third-party brand is 3 for $5, free shipping
(all assuming you are located US, my apologies if not)