Guys, i am trying to get a laminar flow hood working so i can do agar work for my fish to save some cash on treatments when they get sick. I have set up some triple layered cotton sheet as the filter i am figuring to have a WG of around .1 however i am finding no real reduction in contamination in fact it seems to be worse then just working in still air. what am i doing wrong? Cotton sheet can stop a .2 micron virus why can i not get it to stop Rhizopus stolonifer when the spores are over 10 times the size?