I have black soil. The pen is a similar size. There's still a bit of grass, but not much. I throw in a lot of weeds for the ducks to eat, and that takes a bit of pressure off the grass that is in there. However, they are penned up all the time, as I live right by a busy road. This means the duck run can get a bit muddy and stinky. I am considering my options to keep it as nice as I can.