When we had mechanical media in our upflow filter we used black vinyl
screening.
It never went bad.
It did gunk up and last fall I had seepage over the back of the filter.
This year I didn't put it in and when the filter drained after the pump died
there was no gunk down there...
which means it is in the pond and we'll have more to clean out next spring.


kathy :-)
algae primer
http://hometown.aol.com/ka30p/myhomepage/garden.html