It's Hygrophila corymbosa "Augustifolia".
It's a nice stem plant that looks very grassy. It's a nice filler in the background in order to achieve fullness like grass, but it propagates like crazy. Trim the plant when it gets to the top and plant the top a few inches away because the stem that you clipped will bush out with other stems shooting off the the sides.
Arlene
It's Hygrophila corymbosa "Augustifolia".
would have seen the second picture in the begining!
<ahem> yeah, right!