Question about some of the media. I'm a diy guy, and I like to save money. I was at walmart the other night a I was looking for diy media. I found sheets of felt for $.42. Only thing was is that it was recycled from plastic bottles. Is that safe? Another thing I saw was seat foam. The stuff people make seat cushons from. I also think Ima pick up some scouring pads. Didn't think about before I read this article. Any input? I got bio balls, so I got the bio down. I need some mechanical.