I've got a crushed shell driveway, and with all the heavy rains we've gotten, a thick green slime is growing on the sunniest side of it. It looks like something that you see washed up at the edge of the ocean. It's very slippery. I keep raking it up, but it's back the next rain (daily). Is there something I can sprinkle on it that would kill it or dry it up? Nothing too toxic though, I have dogs (and squirrels and mourning doves).