Those squares on the screen I use are 1/2" X 1/2" doesn't mean u got to get that exactly just to give you an idea...And yea you can get at least couple grows out of it...

sounds good with the prices now i usually use three and 3/4 bags per grow at 36 a bag.

That's why I have that container...I start out with one of them 11 lb. bricks...I prefer coco tek...