Use Mare’s Tail (Hippuris vulgaris), an Excellent Oxygenating Pond Plant.
Mare’s Tail (not to be confused with “horsetail”, a pernicious garden weed) usually grows below the surface of a pond and absorbs some chemicals from the water, helping to keep it clear and earning it the distinction of being one of the best oxygenating plants suitable for ponds. Oxygenating plants play an important role in maintaining a pond’s health; aside from “oxygenating” the water, their submerged foliage provide food and cover for the fishes, and they also “limit” algae growth by competing with the latter for minerals and nutrients. This nice-looking leafy plant spreads rapidly and is ideal for keeping the healthy “balance” in ponds. The straight, hollow stems are covered with fine needles of leaf, looking like pine trees. They are known to be suitable for the shallow parts of the pond (0 to 30 cm deep), but are also known to thrive in deeper (70 to 80 cm) parts of the pond as well.