At least in NSW elodea has been declared a pest weed
thus not for sale in aquarium shops
but an alternative, is a plant called "pink baby tears" by the local pet shop.
I was in a pet shop yesterday stocking up on goldfish and when I asked "what is the cheapest aquarium plant?" I was told "ELODEA @$1.95"
And there it was!! a whole aquarium full!!!
It wasnt labelled "pink baby ears"!!!