How do you want to set up the recirc. loop? Do you want the recirc pump to suck from the box and power the downdraft part or have the recirc pump just suck from the box and spray back into the box (and use another pump to power the downdraft)?
IIRC, downdraft skimmers like larger pumps, so I'm not too sure how well a 700GPH pump would work on a downdraft skimmer.
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32"x32"x20" Cube-ish tank
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