I have heard that bio balls are better for fresh water tanks than salt water. If you want a good filtration system in your sump, add live rock to it.
The bio balls would go above the water level, if you choose to use them. Live rock would go below the water level.
I have live rock in my sump. Since I never started with bio balls, I can't say which one is better for keeping nitrates down. From what I've researched, live rock is supposed to do the better job though.
Joe |