Usually takes several days for seeds to pop and surface, perhaps up to a week. I don't know much about Miracle Grow... It may be too "hot" for young seedlings (by this it means that there are too many fertilizers already in the soil), but otherwise it is alright to use. Most people will recommend you to stay away from MG, but you can use it. You just have to remember that you do not need additional ferts in your water for the first couple weeks after each re-pot, as the new fresh soil will have plenty at first.