Bioballs vs LR rubble in Sump.

[fencer]

Bioballs are mean to similate rubble (sort of). They both provide surface area for bacterial growth. They differ as bioballs are more effective at gas exchange and the random path they provide for the water. Rubble channels. Really bioballs are not made to be immersed in water. Any sludge coming off fall into the lower chambers wher it can be siphoned off. They still use bioballs in wastewater treatment facilities. I have bioballs running on the outflow of the tank and the exit stream flows into the fuge with live rock and skimmers.