It's kind of hard to explain....for the short version, (and I won't bore you with the process) I eventually "stacked" them...one inside the other...but I have since, through trial and experimentation, eliminated the 100 and 50 microns from the process....my water just doesn't get that dirty anymore.
I tried a bunch of different experimental ideas and they all had successes and fails....but ultimately, a 300mic inside a 200mic has been the best and most practical. You start getting down to the 100-50-25 sizes and flow just doesn't gravity through. No you have to come up with a way to pump it through....and just an FYI....many people believe, as I once did, that the dark brown accumulation in the sock is fish waste....well, a very small amount is, but what really is clogging the sock is actually the bacteria colonizing the material...that what I have discovered.