I go into the fabric store and buy the batting that is shaped for a seat cushion, they have several thickness's. I put that over my pump in our skippy filter and pull it out every couple of days and it rinses right out without being "soggy" it usually last about 5/6 weeks before deteriorating.

i use felt padding,the thinner stuff does not clog to quick.you can buy it for about 1$ ayard

You can cut batting to size if you want to clean it frequently. Mine has not been cleaned (replaced) in 10 months. My pond (1000 gallons) is completely clear. I will replace it this fall when I close up the pond for the winter. I run my pump all winter. To change the batting I allow the Skippy to drain and the water to settle out of the batting and out of the Skippy drain. The drained material is much easier to handle. I remove it and lay it aside to dry before disposal. I save a small piece to restart the microbe colony. I fold the new batting to fit, stuff it in place with the starter piece under the new material. Then I turn the pump back on. It takes about 15 minutes, maybe 20 if the batting is really dirty.

Polyfill contains short fibers. Those come loose and can get caught around the shaft of your pump. This can burn out the motor of the pump.

Nylon stockings are not as good as cotton or linen bags for Activated charcoal. The mesh seems too fine for some reason.

Update - In the two weeks since my original post, my pond is now clear to the bottom, 24-30". No loose fibers from the fiberfill and no effect on the pump. I clean the bag every 4-5 days and the pump filter every week.

Totally unrelated, the green mesh AC filter in my Skippy is starting to fall apart. I pull a clump of fibers away from the outflow every few days. Anyone else have this problem? There are two pieces of AC filter, one above and one below the bags of scrubbies. I think I'll switch to a sturdier material next year in the new Skippy. Maybe cut the sides out of a laundry basket?