Floss tends to get filled up with gunk pretty quick, and as its designed to filter the smallest particles out of the water, its best to make it the last peice of media the water travels through. Without knowing much about filter you have of course, i dont know where in your filter that is!
Hope this helps!
Ben
EDIT - Googled your filter, it looks like it could be the very last tray, but would wait for someone who knows exactly to advise!
Possibly so, but usually filter wool/floss is enough to remove the worst. I have really hammered my 180 today, scubbed it, vacced it, re-arranged it slightly and done about a 50% water change and quickly rinsed my thin piece of floss in my TT 1200 and the water is crystal and has been since dinnertime.
Were should I put the same wool in my AS620T built in filter, I've read that on this particulacy filter that it's best to go it as the first layer above the black sponge but can anybody shed any light whilst were on the subject ??