A couple of times when I made fruit fly cultures, I noticed that some of the media looks slightly discoloured and a bit powdery looking up close. It does not smell foul and the flies don't appear to be bothered by it. I do see tiny larvae on the sides of the cup. I am wondering whether or not this is a type of mold. The media formula is what Understory Enterprises suggests on their website for making homemade culture media. It is made up of equal parts unsweetened applesauce and mashed banana, whole oats and yeast. The recipe calls for a tablespoon of yeast and to sprinke some on the surface but I only use a teaspoon and I sprinkle a little bit on the surface. This mold-looking stuff only appeared in my hydei cultures and I've never had it happen in a melanogaster culture. In the photo I included, the darker coloured media toward the bottom of the photo is the normal colour whereas the stuff toward the top is the discoloured powdery stuff. Has anyone else experienced this and know whether or not its mold or just yeast and if its harmful? thank you!