I have both and they do well. The blyxa is in a small Spec. It is lush and beautiful I only do root tabs in there. The Spec is small so there are only 3 plants in it.
Stargrass has done extremely well for me in my 40B. I keep it cut to about 5 inches and it is a beautiful hedge. The 40B is dirted. I think the worst part for me is how easy the stems break when you mess with them.
I say they are worth a try.