The present research is a scientific documentation of a historical environmental event. which is the invasion of two species of non-native (exotic) aquatic plants for the Tigris River flowing in Mosul city center near Al-Dandan water purification plant. One of them is Azolla filiculoides Lam. a fern belonging to the family Salviniaceae. https://chefesquipmenters.shop/product-category/water-filtration-systems/