Also known as Vallisneria gigantea and V. americana "Gigantea"
Very long, broad, ribbon-shaped leaves
Green to reddish coloration
Undemanding plant for large tanks
Useful to create a jungle-like atmosphere
 
The Giant Vallisneria is an easy plant that grows fast, suitable for large aquariums. Mostly labeled Vallisneria gigantea and V. sp. "Gigantea" in the trade, the plant actually belongs to the Australian species Vallisneria australis.
In most aquariums the leaves grow so long that they float on the surface (50-150 cm, width 2 cm and above). In these cases the plant needs pruning to stop it taking too much light from plants growing beneath.
The leaves are tough and strong, so they are normally not eaten by herbivorous fish. 
The Giant Vallisneria is easy to propagate using runners, which are prolific if the bottom is nutritious. It grows also at cooler temperatures in unheated tanks.