Identity?

It's Alternanthera. Needs lots of light or it sheds all the leaves below the top node or two. Lovely plant though, given 2.5wpg+. Not tremendously fast growing, I get around an inch a month. The bunch in the picture needs picking out into individual plants; you risk some root damage doing this but this is a stem plant and can recover from that without much difficulty; it doesn't regrow shed leaves.
 
AquariaCentral.com