Botanical name: Echinodorus palaefolius
Common name: Mexican Sword-Plant
Family: Alismataceae
Origin: Brazil
Echinodorus palaefolius has round leaves with a horizontal leaf base. Under water the leaves are narrower and longer. The next leaves will then become shorter and the plant will remain under water. Common as aquarium plants, they grow even larger as emersed pond plants.
Similar plants: Echinodorus palaefolius (Mexican Sword-Plant )
Link to this plant:
https://toptropicals.com/catalog/uid/echinodorus_palaefolius.htm