Several of my sumps are multiple containers connected with 1 1/2 inch hard pvc
They are kind of old school(like the guy that made them),but have worked FLAWLESSY for years!
1 is a marineland model 4 sump with a 29g tank in series,
1 is a marineland model 2 and 2@29g run in series,
Have a large powerhead and hose to pump water back to first section of filter.
I run this pump 1 time a month to blow out bubbles that accumulate in the tubes.
I have pics ,but can't load here so PM me if you want to see.
My top offs for these systems would be 3x as often if I didn't add this extra volume to my filters.