making better use of those rear corner sections

[Esage]

I'd consider going with de-nitrate instead as it does better in lower flow.

I thought Matrix was supposed to work at any flow rate, slow or fast

 

[pompeyjohn]

I just went to check with seachem, and it seems that you are right, matrix does work at any flow rate. My LFS told me something different.
https://www.seachem.com/support/forums/forum/general-discussion/1743-denitrate-vs-matrix

 

[.Marshall]

Update on these problem areas in the Nuvo 40? I have been having elevated nitrate/phos issues and so I cut holes in the sides of the black film and visually confirmed these areas are filled with detritus. I’m thinking about throwing a Nero 3 down there or some magnetically mounted powerhead.

 

[brianfarm6767]

I have recently been trying to figure out how to best use this area in my fusion 20. Not much room there, but I was able to fit about 1.5 pounds of Biohome Ultimate Marine in there. Figured filling it with media in a media bag would at best help with biological filtration of the aquarium and at worst slow down the detritus that would build up in the corners. Taking out the media bag a couple times a year to rinse off would also disturb any detritus that was able to work its way through the bags and media.