You might be interested to note some fairly common aquatic plants which are category I declared weeds which you may not keep : http://www.plantzafrica.com/miscell/aliens2.htm Azolla filiculoides Lam. Azolla, Red water fern.. Weed Egeria densa Planch. Dense water weed. Weed Eichhornia crassipes (C.Mart.) Solms Water hyacinth Weed Elodea canadensis Michx. Canadian water weed Weed Myriophyllum aquaticum (Vell.) Verdc. Parrot's feather Weed Myriophyllum spicatum L. Spiked water-milfoil Weed Pistia stratiotes L. Water lettuce Weed Salvinia molesta D.S.Mitch. Kariba weed Weed (And other species of the family Salviniaceae)
