That's going to take a long long time! 1 pot, lol. Hairgrass can look nice in that style. It depends on what you want, how patient you are & how much $$ you want to spend. Some people grow HC emersed to get it going but it's still slow to fill in & that's starting with a lot more. Hairgrass, in my limited experience, spread but in a more sparse way, takes time to get that dense carpet look.