OK here's my .02
If you want to run carbon....price a filter bag, and a container of carbon and fill your own bags.
Instead of all their foam pads, but some of this poly fiber stuff, and put it in one of the trays
Put some of those ceramic ring things in one of the trays
I have no foam pads in my canisters...BUT I DO NOT KNOW if you have to have some on a smaller tank