Well Elodea Densa is always very well recieved but you need to consider it as sacrificial as they like eating it You could try a combination of real and artificial. Live plants and moss balls absorb nitrAte from the water too You can order online with a discount from Plants Alive from here or use ebay. (My favorite seller is biotopeaquatics)
moss ball and elodea now in place!! any ideas how to stop star from playing football (or is that finball) with the moss ball? she keeps pushing it round the tank till it floats haha