Hornwort

Hornwort is one of the most widely distributed aquatic plants on the planet, found on every continent except Antarctica. It is a rootless, free-floating stem plant that absorbs nutrients directly from the water column through its finely divided leaves, which grow in dense whorls along the stem. This growth habit makes it an exceptional natural filter: it takes up ammonia, nitrates, and phosphates rapidly, helping to prevent algae outbreaks in newly set-up tanks or shrimp aquaria. Hornwort thrives across an extremely wide temperature range of 10 to 30 C and tolerates soft to hard water with a pH of 6.0 to 9.0, a versatility that few aquarium plants can match. It needs moderate light and does not require CO2 injection; in low light the stems may shed their lower leaves, but the plant as a whole continues to grow. Growth is exceptionally fast — in good conditions stems can lengthen by several centimetres a day — and regular trimming is necessary to keep it from overwhelming the tank. No special planting technique is needed: simply place a stem in the water and it will grow. Because it lacks roots, hornwort is also an excellent choice for pond and coldwater setups, and it is winter hardy in temperate climates. Propagation happens by itself — any broken fragment grows into a full plant.