Last Updated on April 23, 2023 by Coral Realm

Hornwort is an incredibly easy plant to grow and keep in a freshwater aquarium or pond. The name hornwort is used as an umbrella for the ten species in the genus Ceratophyllum. However, of the four species the most commonly found in the aquarium industry is Ceratophyllum demersum. 

Having a planted tank has numerous benefits. From providing shelter for fry and smaller fish, to oxygenating the water, plants are a must for a natural, healthy fish tank.

Hornwort is a great freshwater aquarium plant. It is very versatile; it can be grown both rooted in the substrate or floating. This is also a very hardy plant and can survive being trimmed so you can cut it to the length or shape you need. This allows for a lot of freedom and liberties to be taken in how you display it. It also means that a wide variety of freshwater fish species can benefit greatly from a tank with Hornwort. 

Hornwort Ceratophyllum demersum has a cosmopolitan distribution; it is found on all continents except Antarctica. As such it is extremely hardy, quick growing, and easy to care for. The following table displays some basic information about Hornwort:

Hornwort General Information

Care LevelVery Easy
Temperature Range59°F – 86°F (15°C – 30°C)
pH6 – 7.5
PlacementBackground or floating
Grow RateFast
Maximum Size10 feet


Hornwort General Information

Hornwort General Information

Hornwort is an incredibly popular freshwater aquarium plant. It is widely used in a wide range of tanks, and also has very widespread use in ponds.

As we have mentioned above, there are ten species of plant in the genus Ceratophyllum, all of which are known as Hornworts. By far the most commonly used in aquariums is Ceratophyllum demersum, though Ceratophyllum submersum, or tropical hornwort, is also used. C. submersum is most often used as a way of decreasing nitrogen in the tank. Ceratophyllum demersum has a cosmopolitan distribution, being found on every continent except Antarctica.

Ceratophyllum demersum is the species we will focus on here, as if you buy hornwort online or in most pet shops it is this species that is sold. This species has spread throughout the world, and has found itself as a problematic invasive plant in New Zealand. But it is this which makes it perfect for aquariums and ponds. Invasive species are tolerant to a wide range of environmental conditions, and tend to be fast growing and very hardy.

These characteristics are certainly true of Hornwort. It is therefore a perfect plant for beginner aquarists who are looking for plants which don’t need a lot of maintenance. 

Being so hardy and fast growing also makes Hornwort pretty cheap and easy to get hold of. It is readily available online, and in most pet stores. Hornwort is also very popular around the globe as both a freshwater planted and floating plant, which drives demand. The price can depend on the quality of the Hornwort sold but usually a bunch is a very reasonable price. 

Hornwort Appearance

Hornwort Appearance

Credit: marygillhamarchiveproject (Flickr)

A typical Hornwort plant grows from a central base and produces many branches. This can create the effect of multiple plants from only one individual. 

Hornworts utilize rhizoids to anchor themselves into the substrate. They lack true roots, and specialized leaves also function to hold them in place. 

It is a dark green plant; both the stems and the leaves are a beautiful deep green. A lighter shade is generally shown in warmer waters though. 

The leaves are short, about an inch in length, and needle-like, and can fork once or twice. They are produced in whirls running circularly around the central stem, which in general 6-12 leaves per whirl.

In the wild Hornwort can grow to be around 10 feet long. As you can imagine this means that without trimming it can quickly reach the top of your tank if you have it planted. If floated it can quickly grow to cover the surface. As said before, it is a branching plant and generally branches 3 times. 

It is a monoecious plant, meaning that both male and female flowers can be found on the same individual. The flowers are important for sexual reproduction but Hornwort also happily proginates asexually too. Flowers aren’t spectacular, but are pretty in their own right. They are brown in color. Are fertilization flowers form a spiny nut around a fifth of an inch in size. 

Hornwort Benefits

Hornwort gives many benefits to the aquarium. Firstly, it is a good oxygenator of the water. To create energy plants photosynthesize, and the byproduct is oxygen. This oxygen is put into the water where it can be used by the fish and other animals in the tank. 

It is also a very good looking plant. Being aesthetically pleasing it can really take your tank to another level. The deep green color can highlight the color of your fish. As a background plant it can look fantastic, and as a floating plant the light can really accentuate the color. Hornwort catches the movement of the water in a very captivating way. You may find yourself watching it sway in the currents! 

The small leaves and branching stems provides a great place for smaller fish and fry to hide. Shrimp will also use Hornwort as a hideaway. Having a place to feel secure and run from larger bullying fish increases the health of small fish dramatically.  Some fish don’t like a lot of light and prefer shaded areas. Hornwort is great for these fish too, especially when used as a floating plant. 

This plant also helps to regulate the water chemistry too. While Ceratophyllum submersum is better at decreasing nitrogen concentrations Ceratophyllum demersum also had this effect. 

Hornworts also has allelopathic abilities; it can inhibit the growth of other competing plants. This can be very useful in preventing harmful algal blooms, but it can have a detrimental effect on other plant species in your tank.

Hornwort Care

The following section will guide you through Hornwort care in detail. 

Tank Requirements for Hornwort 

The good thing about Hornwort is that you don’t need to have it in mind while setting up your tank. As we’ve said previously Ceratophyllum demersum is found all over the world in different ecosystems. From ponds and pools to rivers and lakes it will happily take hold and grow. So you can be sure that it will find a good home in your tank setup.

It can tolerate a wide range of conditions. The temperature range it can handle is between 59°F – 86°F (15°C – 30°C). This means it is happy both in tropical and cold water tanks. This range also allows it to thrive in outside ponds. It prefers a neutral to slightly acidic pH of 6-7.5, and a water hardness of 5-15 dGH. 

Like all plants it does best in a filtered tank. The filter removes compounds like ammonia and nitrates. Hornwort will act as a natural filter, removing these compounds itself, but as with all things it would be best if the water chemistry was good to start with! 

The large size it can reach and the fast growth rate means that it is best used in larger tank sizes. However this is only because in larger tanks it needs less trimming to keep it in check. In a smaller tank it can quickly grow to dominate if it isn’t trimmed pretty regularly. It can easily be kept in even a small 5 gallon tank, but as said it will need regular trimming.

Hornwort does like a lot of light. So if you have it as a rooted plant make sure the water is clear and that there isn’t anything obstructing light from reaching all of the plant. Water can be kept clear by having a good filter with the three stages of filtration; mechanical, chemical, and biological. 

Especially if you have other plants as well as Hornwort in your tank, the nutrients they use to grow and be healthy can diminish. Using an aquarium fertilizer can help greatly. As Hornwort lacks true roots it takes up most of its nutrients through it’s leaves, so a liquid fertilizer is best. 

Hornwort Maintenance

Being a very hardy plant, the only real maintenance you need to do with Hornwort is in terms of its growth rate. 

While the exact grow rate varies greatly depending on lighting, temperature, nutrients, and grazing, Hornwort can grow at 4 or 5 inches in a single week. 

As you can imagine this can quickly get out of control. So regular clipping and trimming of your plant to the size you want and need is essential. You don’t need to be too careful with how or where you trim it; it will grow back healthy no matter what! 

Hornwort can shed its needles. When you are trimming back your hornwort you may see some leaves fall. This normally isn’t an issue; many fish will eat these as a little snack. The filter should suck up some of these needles, and you can get them when you clean the filter. If they settle on the substrate you can get them by using an aquarium vacuum cleaner.

As we have touched on before, warmer water will make the plant become a lighter shade of green. Brighter light will also make the plant display a light green. So floating Hornwort will more likely be a lighter green than planted, as it is closer to the lighting. Before you play around with the temperature though be aware of the temperature requirements of the fish and other plants in the tank. Many species have narrow ranges they are comfortable in, so ensure you don’t change it out of the range which best suits your setup. 

How to Grow Hornwort – Plant or Float?

As you should have gathered by reading this article, Hornwort is perfectly happy both as a floating aquarium plant or as one anchored in the substrate. Which is the better option is quite suggestive, and depends on your personal tank setup.

You should think about the fish in your tank; are they top or bottom feeders? Do you have labyrinth fish? Do you have a mix of fry, small, and larger fish? 

Planted Hornwort with betta

A betta fish with Hornwort planted in the substrate. Credit: Starr Environmental (Flickr)

If you have a high proportion of top feeders in your tank you may be best suited to planting Hornwort. The same can be said if you have labyrinth fish. These are fish such as Bettas that can breathe air. If you decide to float Hornwort in these cases then it can interfere with feeding, and can get in the way of the labyrinth fish breathing air. Though if properly maintained and trimmed floating hornwort can provide great stimulation for surface dwelling fish, giving them a place to explore.

If you have a mix of fry, small, and larger fish, floating Hornwort can provide more substantial hiding places. Though planted Hornwort also provides a great shelter for smaller fish. 

You should be thinking about what aesthetic look you are wanting from your tank. Both growing strategies have their similarities and differences. While one doesn’t offer a “better” look than the other, they are different. You can also test one way, then if you don’t quite like it or the fish don’t react the way you wish, you can try out the other instead.

Floating Hornwort will provide shade for the base of your tank. This can enhance the colors of your fish, while can help the health of fish if they prefer more muted lighting. Always be careful of filter inlets when floating plants though.

Hornwort Propagation

As you could have probably guessed, Hornwort readily produces new plants. It doesn’t rely on sexual reproduction; it reproduces asexually via fragmentation too. This has enabled Ceratophyllum demersum to be the incredibly successful plant it has been in the wild. 

Fragmentation is when a piece of the parent plant is either forcefully or naturally removed. Each of these fragments then grows and forms a mature plant genetically identical to the parent. 

You can easily recreate this in your home aquarium. Hornwort grows in multiple stems; simply cut off one of these stems and either plant it or float it, and it will mature into a plant of its own. 

You will also find that fragments will split off naturally. It is this along with the fast growth rate which allows it to quickly take over and dominate a tank. 

The fragments which grow into full plants don’t have to be a full stem. Even small pieces of plant can form a whole new mature plant.

Compatibility of Hornwort – Suitable Tank Mates

The great thing about Hornwort is that it is a universal freshwater plant. As long as the temperature ranges align, it can be used in any tank with any fish community. 

Of course there are some fish species that will prefer Hornwort more than others. Live-bearers are especially keen, as it provides a great refuge for fry, and for adults too away from larger more aggressive fish. Some examples of live-bearers that will benefit most from this are Guppies and Molly Fish. 

Guppy Care

Larger fish such as Angelfish and Gouramis will happily utilize Hornwort as a food source, nibbling and biting the leaves. While this can be very detrimental to some freshwater plants, Hornwort is a hardy beast and shouldn’t be too affected by this.

Shrimp and snails will often be found amongst the needles, scavenging for any trapped food. This can be very useful if you have it floating. Snails and shrimp will also help to clear up any shod needles, as will bottom dwellers such as Plecos and Loaches.

Common Issues

One of the most common problems with Hornwort is that without being regularly maintained the growth can get away from you. Especially in a smaller tank the fast growth rate means it can quickly come to dominate the space. 

However regular trimming and maintenance and disposing of the trimmed ends can prevent this. Always make sure you haven’t accidentally picked up small fish, fry, snails, or shrimp when you get rid of the excess.

The fast growth rate and large total size it can reach makes it very popular in ponds as well as in aquariums. But while it can be tempting to leave it to its own devices in a pond, you will still have to trim and maintain it. Otherwise it can grow to dominate the pond as well. 

We have mentioned before that Hornwort can shed its needles. While some of these may get picked up by the filter, and some of them may get eaten by fish or shrimp, some will settle on the substrate untouched. If you leave these needles on the base they will degrade and contaminate the tank. Using a good aquarium vacuum cleaner will enable you to get these up. 

If you find that your plant is shedding its needles at a much higher or faster rate than normal it may be that your aquarium is too hot. But before cranking the temperature down ensure that all your fish and other plants and inhabitants won’t be adversely affected by a temperature reduction. 

Conclusion – Is Hornwort right for your Aquarium?

Basically, no matter what aquarium or pond you have, Hornwort will be suitable. It is a very hardy plant and can grow in a wide range of conditions. 

It also has numerous benefits, including oxygenating the water and providing shelter and safety for smaller fish. 

Another big plus point is its versatility. It can be grown both as planted in the substrate or as a floating plant. 

The way you choose to grow Hornwort is up to you, but know that your tank will be better for it!

You may also like to read the following articles:

  • Best Aquarium Heaters
  • Java Moss – The Complete Care Guide
  • Best Gravel For Planted Tanks

Featured image credit: Starr Environmental (Flickr)

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