You need to purchase a strong fan(turbo) for some added ventalation. This will irritate the "nats" that are bothering you....and they will leave so to speak. If you are using REAL sprouting seeds you need not cover then with anything. I am a commercial grower in Orlando, Florida...this is our 9th year! We use Hard Red Spring Wheat....less yeild but much better taste. What is your water sourse. Some wells have bactierial iron that may help to attrach the nats (bugs). Also it sound like you may be oversoaking your berries(seeds). Oversoaking may cause an aroma that attracks the bugs. I grow over 200 pounds of beries a week...If you are located in Florida and would like to visit...call me at 407 797 6067 my cell phone....and we can set a date for your visit. I will be glad to show you EVERYTHING we do. You may see some of our pictures here in the wheatgrass gallery.