Finally started building a skippy type stock filter, got some of those furnace filters by NaturalAir....the green biodegradable ones from HD. Read something about them breaking down and causing problems so now I'm worried and wondering if I should return them or give it a shot. Also, do I cut them into small pieces or lay them in flat. I'm also going to be adding some scrubbies and other stuff too on top of that. Thank you.