interesting enough i have a 40 breeder sump so i thought i would share alittle on mine.
my dementions are:
| skimmer section; alittle shy of 8'' | BT | Return; 6'' | BT | Refuge; 17''
the bubble traps make up the remainder, theres 1 inch between each plus the thickness of the baffle, i also added a rectangle inlet on the refuge side so my water is slow flowing in this area. its a simple 8''x3'' rectangle that the water flows into, over and through the fuge.
i used 3/8ths acrylic actually polycarbonate that i picked up cheaper then the thin stuff at a hardware store from a sign company in PA that sold is as "scrap"
the rock in the fuge was in another tank but recently just added it to the system as shortly ill be switching everything over to the new setup
heres the best i can get of the inlet rectangle i mentioned
heres the skimmer side with carbon/phos reactors and where the pump, pumps water out to the skimmer and flows back in, if you have an out of sump skimmer you can cut back on the room needed in the skimmer section
and the MRC-MR2 skimmer
have you picked a skimmer out yet or thought about models?