Pay attention to your base.....If its going to be covered with grass....plan on making it mowable or it will quickly get over grown. You will spend more time clipping grass than messing with your tanks. If you are going to make it a sand or clay base, you might want to lay down some weed blocking sheets and spraying some grass/weed killer. If you are going to add some hills and "rivers"....plan it out how you are going to mow it. Nothing worse than making some nice hills and then chopping the tops off them when you mow...don't ask mehow I know this...lol