The pores on this filter bag are 10 microns, by contrast a human hair is about 40 microns. The bag hangs on the inside of the reservoir and my intake is at the bottom. Nothing gets in. I have been running without a clog for over a year.
You can wash and dry these and they are tough. This filter should last for years.
10 Micron 7″x16″ Singed Polyester Felt Filter Bag Update
I have been using these felt filter bags for years and still have my originals. Over time I found you can use a larger mesh like 50 and still not have dirt get in. The only reason I changed is that the pores are so fine that they can start to clog with some nutes. If you don’t clean the bags this can restrict water flow to the pump. So I would probably recommend the 50 mesh felt filter bag at this point cleaning or replacing them them from time to time too.