Sump setup

[guitarvp]

So I picked up a 34 gallon tank w/ stand and a 5g sump today and plan on moving my 20g over in the near future. I currently have an AC-70 HOB refugium on my 20 and want to build a fuge into the new sump. This sump has a separate box/chamber that stacks on top of the main chamber and that the overflow pipe feeds directly into. So my questions are: should I run a filter sock out of the overflow pipe into that top chamber? What should I fill this top chamber with, bioballs/crushed coral? Attached is a picture of the sump. Any suggestions are appreciated.

 

[Andrew McFadden]

Id put a sock on it for sure