I find that a lot of people call that pearl grass stuff HM. I actually ordered pearl grass thinking it was HM one time and was very disappointed to see what I got. Anyway I have since found one stem of HM in a bunch of rotala indica and now from one stem I have almost a full carpet of HM and I love it.
With the right light/nutrients/co2 you will find the love of this stuff that I have.
Fishymatty - That's how I got the piece I have. It came with a bunch of Rotala Indica. lol. Thats why I thought it may be Rotala initially. It was so tiny at first, I almost threw it out. Glad I didn't.