I just wondering if anyones found a solution to permanently get rid of black flys. Ive been having problems with them for over 8 months now and ive had 7 plants die on me. Ive been using pyrethrum 5EC and it seems to kill them but they keep coming back. I grew in nft tanks and i have changed to aqua farms and still have them. I read u can smother them if you put a layer of sand over the top of your soil, but as i grow in clay pebbles this wont work. Any ideas Help!!