I've never heard that.
According to Rena, the lower basket on my XP2 has the three grades of foam, coarsest first on the bottom, then medium and finally the finest on top.
Top basket has a compartment for Starz (bio balls) in the bottom part, then the chem zorb (or whatever they call it. carbon) then the white water polishing pad on top.
I don't use the carbon, I substitute poly fil pillow floss (not the flame proof treated kind).
Fish poop will generate beneficial bacteria, but I've never heard of it being used on bio balls. Why don't you set up your filter like the factory recommends?
After that you can experiment with the media/bio balls, etc.
Charles