whats the best air fliter!!

ive put a 3rd fan in the top chamber of a p182 case but cos ive moddified it a bit there no air fliter so i fort i'll ask u guys wats the best thing to use as a fliter?i bort a schyle slipstrem 110cfm!!

Black panty hose. I put little squares of it on my 900 after I figured how lazy I was after not cleaning it for a month and my video card overheated. The inside is now squeeky clean. A little unorthodox, but it works for meh.

Edit: The suction is enough to hold it in place if you were wondering how I put it on the front and rear fans lol.

I use A/C foam filter mat. on my rads. I just cut it to the size I need and hang in in front of each rad. I have 2 sets and change them out every week and wash the dirty one for the next swap. Lowes sells this stuff for under $2.00 a sheet.