You could run a closed loop system and then "T-out" the connections from the pump. That way you would have several returns all from the same pump. Although you will need more than one pump for a tank that size. You could use your one pump and then put in some powerheads.
I'd use powerheads if I were you. Not sure how much of a factor cost is, but powerheads are pretty cheap and they move a lot of water....