Hornwort, also known as Coontail, has sturdy, layered hair-like foliage that helps oxygenate and clarify the water as well as keep algae growth to a minimum. It is found free-floating worldwide, in moving and still waters, or loosely anchored in muddy bottoms. Hornwort leaves are dark green and grow from a 1/2 to 1-1/2 inches long on stems that can reach 24 inches in length. These plants have lead weights and can be simply tossed in your pond and will sink to the bottom. Hornwort typically winters over in zones 5-6 or warmer. While koi tend to devour many plants, they seem to leave hornwort along. This is part of our formula for crystal clear pond water.