Where should I put some floss ??? In my sump

[Delphinus]

I'd say anywhere where it can be guaranteed that flow goes through the floss and not just around it .. and yet can harmless spill over when it eventually gets clogged. Only tank I run floss on myself is my FW tank and I have it where water enters the sump. When it's time to change out it just spills over into the sump.