Problem is, if the floss is pulling the stuff out, its STILL in the tank decomposing and adding to dissolved organics until you remove the floss and clean/replace it. That is the main reason I don't use a filter sponge in my overflow. You know what they say, out of sight out of mind, and in my case its true, I'd forget about that sponge after a couple weeks and slowly the flow thru my sump would slow, and dissolved organics would rise. Not a good thing.