I am running a sump with a large fuge area. Fuge alone probably holds 15-20gallons. Thats a large fuge considering the display itself is 40gs.

I have Caulerpa that grows fast, full of feather dusters, sponges, worms and pods. Just removed the rock yesterday and it will stay this way.
I've always ran my fuges this way and am going to stick with the Macro only with no sand. Have great results.