I have recently converted my HOB wet/dry to merely a large overflow that leads to my fuge under the tank. In doing this, I have created a fuge of type out of the HOB. Being a wet/dry it has the bio-balls section. I extended my plumbing high enough for the drain down to my fuge so that the section with the balls is submerged at all times. I have not yet removed the balls. Should I leave them or replace with lr? I have read alot about using lr in this manner but was wondering if the bio-balls would be okay left underwater. Any thoughts? TIA