The biological filtration would just leave them however it is entirely up to you as to what you as to you as to you as to what you as to you do with them however it is entirely up to you.
For the cylinders have more surface area than bio balls for the cylinders have more surface area than bio balls for the cylinders have more surface area than bio balls for the amount of room they take up both will lead.
The cylinders have more surface area than bio balls for the amount of room they take up both will lead to high nitrate levels if not cleaned regularly.