Middle sump setup?

[Heres_doe_]

I’m in the process of putting tank up once again. I will be running a trigger sapphire 36. Middle compartment will have a diy algae scrubber over it. Now what would you put in the actually sump. Bio media? Miracle mud? What’s your input

 

[VintageReefer]

I have a trigger ruby 30. My middle section is 3” sand bed, lots of live rock - both big pieces and rubble. And a algae scrubber