SubstrateSource Vallisneria Americana VAR. biwaensis &ldquo;Corkscrew&rdquo; Live Aquatic Aquarium Plant SubstrateSource Live Aquatic Aquarium Plant. Great for middle and background zones. Does not require high lighting or CO2 supplementation. Easy care in a mature aquarium. Can be sensitive to sudden changes in water chemistry. SubstrateSourcePlant Guide included.