It's perfectly fine for water to go around the
media bags, because some water is still flowing through the bags.
I have a
FX4 and FX6 and they flow a lot of water.... I used to run
Purigen as well in my larger
Aquaclear HOB and they always needed to be recharged more often that I liked.
Consider how long the Purigen will actually last when running in a FX6. It probably will deplete quicker than you think.
Are you going to run carbon and Purigen in these fine bags, or something else?
In the past I would buy the bags of Fluval carbon made for the Aquaclear 110 when I found them on sale
on Amazon or Petsmart online. After running the carbon for a month I would cut a slit at the end, dump it out and refill the bag with something else. I would either reseal it with some needle and thread, or just twist the end and secure it with a plastic zip tie.
I have also bought some zippered media bags from Amazon (I believe the
Aquaneat brand) and Petsmart (TopFin) that work decently.
Now days I don't run chemical media anymore, but it does has its uses.
If you want to make your own
Chemi-Pure Elite, Dr. Novak on Youtube has a video where he mixes GFO
phosphate reducer,
activated carbon and bulk ion-exchange resin and puts the mixture in fine mesh zippered bags...