Unfiltered 500R Side Fan

[techtte]

So, I have my new PC for about a month now and it is already really dusty inside. I think it's because of the 200mm fan on the side which is unfiltered. What should I do in this situation rather than turning the fan off?

 

[C12Friedman]

Solution isn't cheap (that I could find) from FrozenCPU but you want to keep using the fan so here ya go...
http://www.frozencpu.com/products/13275/ffi-76/DEMCiflex_200mm_Magnetic_Dust_Fan_Filter_-_Round_-_Black_-_Steel_Aluminum_Plastic_Chassis.html?tl=g47c223s1092

I am personally looking for 1/8" open cell foam to fashion my own filters - a bit cheaper I think (but how to hold them on?)