The drain from the tank is split in two (with a T, plus ball valves), one end goes to the skimmer compartment, another goes to the fuge... so the fuge flow is adjustable. I figure the total flow through the sump is around 600 to 700gph (I'm using a Mag 9, which pumps 900gph @ 3ft, but it's dialed back a bit). The fuge is getting maybe a third of that flow, so around 200gph.
Nuno