well i would agree but usmc mike told me they were no good, ask him for the reason whyAndre said:say what. bio balls are almost found in all reef tanks that i have seen. Even in refugiums there are still a few. If this is wrong i would like to know. I will need to do something different. But in my sump the water level is on bottom of the bio balls acording to the sticker and that was a pro clear system.