Well, I don't know if it's what you want, but my backyard is kind of in a swamp, and I have growing out there 2 types of grass that closely resembles hairgrass, but maybe a bit thicker than it. One type grows about 8 " tall, another gets about 12-15 inches and big around. I put a clump of the small type in my tank to see what it would do, and after a month it actually is looking better, getting a bit greener now. If you'd like I could get another clump and let you try it, no charge, just know that it came directly out of the ground, . well mud really and it being winter it may look a bit off but in the summer it's all covered in water, that's why I tried it to start with. Can't guarentee it will grow or anything though, being grown emersed, but hey, could be worth a shot anyways.