Aquarium plants Caresheets

Hornwort (Ceratophyllum sp.) Care Sheet

Last Updated November 25, 2020
hornwort plant inside the aquarium

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Hornwort is one of the easiest freshwater aquarium plants to start off with and is also a favorite among seasoned hobbyists. These fast-growing plants thrive in low tech conditions and can help keep aquariums free of algae. However, their growth rate can become a nuisance and regular pruning will be necessary.

Keep reading to find out everything you need to know about hornwort care and growing members of this genus in your own freshwater aquarium!

Hornwort Care Guide

Name

The Ceratophyllum genus is widely referred to as hornworts or coontails. As of August 2020, there are only about six accepted species within the genus. These are Angiosperms, which means that they will produce flowers in optimal conditions.

Ceratophyllum demersum is most commonly seen available in the aquarium trade, though other species may also be seen from time to time.

Natural habitat

Hornwort can be found in most freshwater ponds and lakes around the world besides Antarctica. Ceratophyllum demersum is believed to be endemic to North America, where it thrives in warm, slow-moving waterways.

As a whole, the Ceratophyllumgenus is considered as an invasive species. Ceratophyllum demersum has heavily affected New Zealand by interfering with the functionality of some hydroelectric power plants. Fast-growing invasive plants like hornwort can also easily take over entire ecosystems; most endemic species are unable to outcompete the fast growth rate, which eventually chokes out and kills native plants.

Is hornwort good for ponds?

Hornwort is regularly introduced into ponds by way of planting or natural introduction. All plants provide benefits for aquatic ecosystems, but hornworts are especially favored for means of additional aeration and nutrient export.

Even under some of the most unideal water conditions, hornwort usually finds a way to thrive and take over the ecosystem (which can sometimes be a bad thing, but we will discuss that later). In moderation, hornwort will provide oxygen through photosynthesis and take up both major and minor nutrients in order to grow; these nutrients are usually problematic for fueling algae, but hornwort is able to use these nutrients before algae gets the chance.

It is believed that hornwort also has allelopathic abilities, though it has yet to be fully confirmed within the aquarium hobby. These allelopathic abilities allow the plant to be able to produce certain biochemicals that can influence both the growth and germination rate/success of other plants and algae. For now, these effects are mostly understood in larger aquatic systems.

Though hornwort is especially popular in pond settings due to its rapid growth, these species can also be used in the aquarium setting to help with additional aeration and nutrient uptake.

Identification

Hornwort is relatively easy to identify, especially since not too many species within Ceratophyllum are readily available in the aquarium hobby yet. The most common type of hornwort to come across is Ceratophyllum demursum. This species can very easily grow up to 2 feet (61 cm) in favorable conditions!

hornwort in black background

These plants are a vibrant green, and actually look like they’re glowing under higher lighting and clear water. They are known as ‘coontails’ due to their puffy appearance that resembles that of a raccoon’s tail. These plants grow by sending out separate shoots, which help to form their overall bushy appearance.

The bristle-like leaves grow in whorls of six to twelve, adding to their bushy characteristic. These bristles can be delicate when being handled, so it is not unusual to see some bare areas along the stem of the plant. Hornwort may also look bare or not as fluffy if nutrients or light is lacking in the tank; this may also be accompanied by yellowing or browning leaves.

Keep in mind that hornwort does not grow roots. If you see a floating plant that is bright green and fluffy and doesn’t have any visible signs of root growth, it is most likely hornwort!

Hornwort tank requirements

Hornwort is very easy to grow and is a favored addition to most low tech tank setups. As this plant naturally grows in many conditions throughout the wild, exact parameters are not usually needed.

Hornwort can successfully be grown under almost all lighting systems, from low to high; it should be noted that while this plant is regarded as hardy, it might start to shed under lower light conditions. It can also be grown in a wide range of temperatures and has been kept anywhere from about 60-85° F (15.6-29.4° C). However, because these plants are such fast growers, they will do best when supplemented with additional carbon dioxide and fertilizers. Though it is entirely possible to have a thriving hornwort plant in the aquarium without these additional aids!

It is also important to keep in mind that hornwort can easily grow up to 2 feet (61 cm)! While hornwort can be grown in smaller tanks, it will need to be regularly pruned and controlled. This is why we recommend a taller fish tank that is at least 12 inches (30.5 cm) tall to start.

Is hornwort a good aquarium plant?

There is some discussion as to whether or not hornwort is a good plant to have in the aquarium. While this fast-growing species helps combat algae, oxygenate the water, and fill up empty spots, it tends to grow just a little too fast sometimes.

Benefits of hornwort

Hornwort is a popular plant in both the aquarium and in the pond setting due to its ability to take up excess nutrients, oxygenate the water, and provide shade and shelter for fish and other aquatic life.

Nutrient uptake

In order to grow so fast, hornwort relies on a constant influx of nutrients. This rate of uptake is usually faster than that of algae, which leads to more growth of hornwort as opposed to more growth of algae. In most cases, a healthy population of hornwort can completely outcompete algae and prevent it from taking root in the aquarium.

As mentioned before, it is also believed that hornwort uses allelopathy to biochemically inhibit certain species of algae and bacteria from growing. Though this has yet to be fully proven in the aquarium setting, these abilities, in addition to their ability to quickly uptake nutrients, make hornwort a popular natural choice for combatting algae problems.

Oxygenation

Like all plants, hornwort undergoes photosynthesis; this is when plants use carbon dioxide, water, and light to produce glucose and oxygen. This process is fundamental in aiding hornwort’s fast growth rate, meaning that oxygen is being produced as a byproduct. As a result, hornwort is an easy and natural way to add oxygen to the water column for fish to use.

Shade and shelter

Lastly, hornwort provides large forests for fish and other aquatic life to find refuge. Hornwort is a popular plant to keep in breeding tanks especially as young fry find safety from predators. Larger fish will also find protection in floating hornwort or swim in out and out of planted hornwort!

If you have a tank with a high light system, you might find that you have too much light in some portions of the tank. Hornwort can be used to block out some of that light and is much more manageable to remove than some other smaller floating plants, like duckweed and frogbit.

Disadvantages of hornwort

There are some cautionary tales to be aware of when picking up your new hornwort. While these plants can be great in some ways, they often require regular pruning and can be frustrating to securely plant.

Regular pruning

Since hornwort grows so fast, it needs to be controlled. Some hobbyists consider hornwort to be a nuisance weed as it takes up all the nutrients in the water, blocks out other plants from getting light, and quickly overgrows anything and everything in the tank.

If you’re planning on adding a hornwort plant to your fish tank, you should be prepared to have to prune it every couple of weeks to keep it from taking over everything. When first added to the tank, the plant may also regularly shed its leaves from its stem which can be difficult to completely clean.

Planting frustration

At first, you might not think that the act of planting hornwort could cause you to hate the species, but as many hobbyists soon find out, it can turn into a massive headache.

Hornwort doesn’t grow roots and does not want to anchor itself. However, if your aquarium already has floating plants and/or if you want your new hornwort to be the backdrop of your setup, get ready for some frustration when trying to plant it.

It may take several attempts to successfully anchor your hornwort plant into the substrate; and even then, make sure not to touch it ever again as it will surely come free and find its way to the top of your tank again! Some hobbyists have even had problems where the buried stem begins to rot, which can cause poor water conditions and lead to further problems with fish and invertebrates.

Though you might not purchase hornwort with the intention to float it, you may find yourself giving up and letting it do its own thing.

Should you float or plant your hornwort?

Most hobbyists will agree that it is easier to let your hornwort float than to try to plant it in the substrate. However, floating or planting your hornwort comes down to a personal preference and which method best suits the fish you have in your aquarium.

Can hornwort grow floating?

Floating this plant is the preferred method of keeping hornwort, and you will find that it is very stubborn to weigh down otherwise. As mentioned before, these plants don’t produce roots, so your hornwort will not shoot out roots in hopes of attaching to a surface.

However, hornwort will quickly take over the top of your aquarium and will need to be pruned regularly. It is also important to watch out for your equipment as hornwort can easily become entangled as it grows!

Can hornwort grow in the substrate?

Though hornwort is usually used as a floating plant as it does not grow roots, many hobbyists have had success weighing down their plants with more fine-grained substrates and rocks. However, some hobbyists have also found that the bottom of the plant tends to rot when planted too deep in the substrate.

While hornwort does not grow roots, this plant does grow rhizomes; rhizomes are horizontal stems that are able to generate other stems that subsequently turn into connected plants of the same original plant. These rhizomes allow hornwort to grow in bushy patches and help anchor themselves in the substrate.

Aesthetic

It won’t make too much of a difference if you decide to float or plant your hornwort; it ultimately comes down to personal preference. If you’re going for a lush backdrop, then it would best to plant your hornwort. Make sure to give it plenty of space as it will quickly fill out the back of your fish tank and the rest of it too!

If you want a more shaded aquarium or like having plants on the surface of the water, then floating your hornwort will be better than planting it. If you decide at any point that you would rather plant it or vice versa, it should be easy enough to make the switch!

Fish in mind

Aesthetic aside, hornwort can be a great addition for fish. You might want to keep your hornwort floating if you have fish that prefer the upper water column as they will appreciate the protection. If you’re trying to breed fish without a separate breeding tank, you might also want to consider floating hornwort as it creates the perfect place for fish fry to grow.

Otherwise, middle and lower water column fish will appreciate planted hornwort that they can weave in and out of and escape the light during the day.

Hornwort pond requirements

Hornwort is a very popular plant to grow in outdoor ponds. This is because it quickly takes up excess nutrients, oxygenates the water, prevents some algae from growing via allelopathy, and provides shade for fish and other aquatic life.

In the wild, hornwort is mostly found floating in calm ponds and lakes; if the water current is too strong, the hornwort plants could be forced under the water, damaging the leaves and stems. Once grown in a bunch, hornwort tends to stick together and naturally sinks deeper into the water column. Some pond-keepers like to attach weights to their plants so that it sinks to the bottom, though some hobbyists have said that this can lead to rot. Like in the aquarium, this plant grows well under most light and temperature conditions

Whether you choose to float or sink your hornwort, there is little extra care needed to make sure that your plants grow as fast as they can. Even if you live in a colder region, hornwort will drop buds before harsh winter conditions begin. These buds will then survive the winter and form new plants the following spring.

Hornwort pond and tank mates

Hornwort is compatible with almost all species of aquarium and pond fish, even those that might pick at plants from time to time! Some hobbyists find that koi and goldfish especially take a liking to hornwort and might cause mysterious empty patches to happen in the pond. However, this plant will quickly replace itself and grow into a jungle for your fish to swim through and explore; it might take a couple of seasons for your hornwort to completely establish itself!

Propagating hornwort

Hornwort may be one of the easiest plants to care for and to propagate. This plant species can undergo vegetation fragmentation, which means that only one plant is needed to create another new plant; all that is needed is a healthy piece of the mother plant.

In order to propagate your plant, simply cut a portion of the stem and allow it to float or plant it in the substrate. Within a few weeks, it should continue to grow just like the original plant.

Conclusion

hornwort aquatic plant in freshwater pond

Hornwort is one of the easiest plants to care for in the aquarium hobby. Right now, Ceratophyllum demersum is the most widely available species but is a great choice for exporting nutrients, oxygenating water, and providing shade and shelter to fish. While a fast-growing plant, hornwort can and will take take over aquarium systems or ponds when left unmonitored, and regular pruning will be required.

If you have any questions about keeping hornwort, if hornwort is right for your tank, or if you have experience keeping these plants in your own aquarium, don’t hesitate to leave a comment below!

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