Personally, I removed my bio balls, had them on overflow , trickle down to sump.
I i used filter wool instead to collect weekly the debris, and throw that layer away. I used coral chips in my sump, and have a separate tank (refugium) : chaeto,grapes algae, ulva algae, and live rocks ........
I read in a few websites that bio-balls are bad ( unless u have the time to maintain/wash them!) which I dont want to....the result speaks for itself! At least for me