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How to Care for Hornwort in Aquariums and Ponds

Hornwort is a popular aquatic plant for both fish tanks and outdoor ponds because of its fluffy-looking stems, extremely fast growth, and ability to consume excess nutrients from the water. Learn about the care requirements for hornwort and whether or not it’s the right plant for you.

What is Hornwort?

Ceratophyllum demersum is known by many common names, such as rigid hornwort, hornwart (a frequent misspelling), and coontail. It grows very tall in the wild and will easily reach all the way to the top of your aquarium or pond. Normally hornwort is found floating at the water surface, but when planted in the substrate, it looks like a fluffy underwater bush with many long branches or side stems. The bright green leaves are thin and rigid, similar to pine needles. Much like water sprite and java moss, hornwort has dense foliage that provides excellent protection for baby fish and shrimp.

Where is hornwort found? Hornwort can survive in a diverse variety of climates and is found on every continent except for Antarctica. It prefers to grow in still or slow-moving bodies of fresh water that contain lots of organic nutrients in the water column.

Does hornwort clean water? Fast-growing plants like hornwort are good at “cleaning” aquarium water because they consume waste compounds from the water (e.g., ammonia, nitrates, and phosphates produced by fish waste and excess fish food) and use it to grow more leaves. With enough light and nutrients, hornwort can easily grow 1-4 inches (3-10 cm) per week.

Do snails eat hornwort? Aquarium snails are detritivores and do not eat healthy plants but rather dying leaves and other organic debris. If you see a pest snail eating a plant, most likely the plant has some unhealthy leaves that the snail is cleaning up for you.

Do goldfish eat hornwort? In general, plant-eating animals (such as goldfish, koi, African cichlids, and turtles) do not eat hornwort. Possible reasons could be the slightly serrated leaves, hard texture, or taste that makes it unpleasant as food.

close up of hornwort leaves

Hornwort leaves are not completely smooth but have small bumps that give it a slightly spiky texture.

How to Care for Hornwort

This aquatic plant can live in a huge temperature range from around 50-85°F (10-30°F), so you can put it in tropical aquariums, cold water tanks with no heater, and outdoor ponds (where they can often survive the winter season depending on your climate). Hornwort grows best as a floating plant, where it has greater access to light and carbon dioxide from the air. Some people like to plant it into the substrate or attach it to hardscape, but because it never grows proper roots, the attached end tends to rot away. Make sure to prune back your hornwort if it starts growing out of control so that it won’t block out the light if you have other plants or limit gas exchange at the surface if you’re keeping fish.

Hornwort tends to prefer gentle flow, so make sure the needles don’t accidentally get sucked up by your filter intake. It can grow under low to high light and does not require carbon dioxide (CO2) injection. Because it grows so quickly, it’s best to use it as a background plant in larger tanks (unless you have the time to constantly trim it). In addition, the fast growth rate means it will quickly drain your aquarium of all nutrients, so you may need to regularly dose Easy Green liquid fertilizer in the water column to ensure that the other plants get enough to eat.

Why is my hornwort shedding its leaves? Hornwort sheds needles anytime there’s a major change in water parameters or it’s kept in an unfavorable environment, such as strong currents, not enough light (especially at the base of planted stems), lack of nutrients, or dosing of certain chemicals like liquid carbon. The most common occurrence is when you first add it to your tank and the plant is not used to your water conditions. Don’t throw away the whole plant, but instead wait for it to recover and it will quickly begin growing new leaves and shoots. Also, make sure to gravel vacuum the fallen leaves to prevent excess nutrients from building up in the aquarium.

floating coontail weed in water

Hornwort is easily propagated by trimming off a section and floating it in a new fish tank.

How to Propagate Hornwort

In the wild, hornwort can form little buds that drop to the ground during the cold season and sprout when the weather warms out. At home, the most common method of propagation is to cut off a side shoot or trim off the top of a tall stem. Any segment of hornwort will quickly become a new plant if you let it float at the surface or plant it in the ground. In fact, one of the easiest ways to get hornwort is to ask around and see if any local hobbyists have some extra trimmings to give away, which they are usually more than happy to share. We do not sell hornwort because it doesn't survive in shipping very well, but we have a whole collection of our favorite beginner plants for you to browse.

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