Sump and fluval 405

[Mark S]

Hi
New to saltwater
I have setup sump Leads into rowa carp with skimmer section
Dsb section and return section with phosban
150. But I also have a fluval 405 canister
I also want to use as a backup. I was
Going to use to act as pump for my
Phosban will prop will not pump as towers above
Sump. Will still use as a filter screen.
Can you tell me which media I should
Keep in canister as a filter screen