Heres my first one.
I cut up some carbon filters for my Weller solder smoke absorber and stuffed them in the 5.25 blanks in front of the fans. I had bought 5 packs of them, not knowing they were 3 to a pack. I also tried the foam that was in the bottom of my mobo box, but it was more restrictive (plus now the air going into the pc is carbon filtered, so pointless YAY!

).
I used a really botched way of measuring airflow and the filters essentially make the tri-cool fans flow the "L" amount of air at the "M" setting, but the filter muffles the sound a bit so its almost a wash.
I may replace it if I can fid less restrictive filter material, but so far this seems to work ok and a shop vac to the front of the 900 should clean it up.
So far so good.