What ppi Poret foam to use?

[bradleyheathhays]

Planning out this canister filter and the bottom trays gonna be three grades of foam filter. Top later in the trap will be some floss while the first two will be grades of Poret foam. In the 1" thick size Poret offers 10, 20, and 30ppi. What two sizes should I use?

[elephantnose]

I'm my Rena filstar in doing two 20ppi and two 30ppi in the bottom tray.