Looks like Rotala indica (false) to me, which is a fast growing stem plant under most situations. After many trims it gets unsightly. Then you can pull it all out and replant the tops. Sounds pretty labor intensive.
its not growing very fast really, but then again i dont use any kind of ferts or co2. i will try and get a better pic later. when i way small tank im thinking maybe 12 inches long and about 6 inches wide
im happy just knowings its some kind of rotala lol. it used to have more of a pinkish tint to it. but after the move it has stayed green kinda silvery under the leaf when i snipped 2 this after noon.