I have been growing grass for my little guy and all of a sudden there are little black flies on the dirt in his enclosure. I am using a top soil from the garden store and grass seeds. I have had the soil in there for a month. I was wondering if I should bake the soil before using it. Or is the soil too old? Should I freeze the seeds before planting them? Oh the flies look just like fruit flies but I dont have fruit in my house.