u want a grass like plant ? i know lots of plant like dat...
but i recommend u try sagitaria sabulatta......it's a very easy and undemanding plant for me.....
otherwise u can try echinodorus tenellus.....
dat's for foreground plants....
if u insist to buy vallisneria, the small kind is vall nana or vall spiralis....vall gigantae will be much bigger unless u put it as a background.....
but if u have skill enuff...mayb u can try hair grass / eleocharis family....
in my 160 litre tank i use sabulatta and tenellus as foreground...vallisneria spiralis and vall nana as background....
rgds,
Teddy - indonesia