Suggestions for empty compartment in nano

[Mark75]

My wife is setting up the new Fluval Evo 13.5 gal. and does not plan on using the protein skimmer which leaves and empty compartment. My plan is to fill this compartment with Seachem Matrix. The tank has a small amount of live rock and I would think this would help with keeping nitrates down. Any other suggestions?

Here are some pictures to help you understand, one shows without skimmer and one with. [emoji3]

 

[LetItReef]

If there's a good flow in that area, I would put a bag of Chemi-pure.