Hornwort: What To Know Before Buying This Plant

Are you looking for a hardy plant to keep in your aquarium? Hornwort is a popular aquarium plant that is well known for their ability to grow under a wide range of water parameters. This makes them well suited for beginners who are keeping live plants in their aquarium for the first time.

If you want to keep Hornwort then keep reading to learn everything you need to know…

What is Hornwort?

Hornwort is one of the many different names given to this plant. Their scientific name is Ceratophyllum demersum and they are also commonly called coon’s tail or coontail. It is important to know that there is another less common plant (bryophytes) that is also referred to as Hornwort – we will not be discussing this plant today.

Hornwort originated in North America but since their discovery it is now found all over the world (except Antarctica). They are actually considered an invasive species due to how easily they can propagate.

This hardy plant can grow in a wide array of conditions, including tropical and coldwater tanks, and even low light conditions and polluted waters. It is a great low light aquarium plant.

Hornwort also rapidly absorbs nitrates and ammonia which makes them ideal addition for most tanks to help reduce the amount of waste. Whilst it is commonly used as a floating plant, they can be anchored to the substrate too.

Despite their appearance they are a type of flowering plant and can produce seeds – although this is rare to see in home aquariums. Most Hornwort are a yellow-green color and you can buy a sizeable branch for as little as $3.


Hornwort is easily recognized. They have a main stem that sprouts side shoots. The leaves are not completely smooth as they have small bumps. You will find the leaves are whorled around the stem in bunches of 6-12 leaves. Towards the end of Hornwort the whorls are more tightly packed and shorter when compared to whorls at the base.

close up of hornwort leaves

Stems can reach up to 2 inches in diameter and can easily reach 2 foot long. They grow very rapidly and each new stem that grows will need to be properly maintained to make sure they do not take over the tank.

Interestingly they do not have true roots, so instead they grow a rhizoid which look like and function as roots. Most Hornworts are a dark olive green. However in warmer high light environments they become a yellowish-green shade. Their flowers are usually different shades of red, pink and brown. They are fairly small (2mm) and are found at the base of the leaves.

Size and Growth Rate

With the right conditions a Hornwort plant can grow around 2 inches per week. Most will reach around 2 foot long in an aquarium. However in the wild they have reached over 10 feet.

Compatibility and Tank Mates

Surprisingly, Hornwort is compatible with herbivorous fish. This is because their leaves are just unappealing for most herbaceous fish like Goldfish, Gouramis and African Cichlids.

However even if your fish happen to nibble on the plant, Hornwort grows so quickly that it is unlikely that they will be completely devoured. Any consumed plant matter will quickly grow back in a matter of days. Snails, shrimp, or other detritus feeders can eat the falling leaves – this is helpful as it prevents the decomposing plant matter from leaching waste products into the tank environment.

With other plants, Hornworts exhibit allelopathy. This helps to stop the growth of algae in your tank. They will not directly kill other plants. However, since Hornwort more readily absorbs nutrients they can outcompete surround plants. As a result, they will slow the growth of other plants. You will need to use carbon dioxide and liquid fertilizer to help your other plants grow.

Care Sheet

Although Hornwort is very hardy there are still some aspects of care that should not be overlooked. When you first get your Hornwort you should rinse it with treated water and quarantine it before adding it to your main tank.

They are notorious for carrying other organisms along with them. Often these pests are unwanted so taking the steps to remove them now will save you trouble in the future. Also whilst they acclimate a lot of shedding can occur.

Having all this occur in a tank away from your main set up will make cleaning this mess a lot easier. A few weeks in quarantine should be enough for both the pests to be removed and the plant to get used to a new environment.

Water Conditions

Hornwort will survive in just about any tank size but keeping it in smaller tanks will require more frequent trimmings and re-adjustments. You should try to choose a tank that is at least 15 gallons to give this plant enough space to grow.

A filter is required for all aquariums but there are some things you need to consider if you have Hornwort. Their leaves will shed and can be inadvertently picked up through your filter. This will lower the flow rate and overall filtering capacity of your tank, so be sure to clear it every once in a while.

For substrates you can have a bare bottom as Hornwort does not have roots. They can survive in a wide range of parameters:

  • Temperature: 59-86°F
  • Water Hardness: 2-25 dGH
  • pH: 6.0-7.5

Light Requirements

Hornwort is not particularly picky when it comes to light requirements. They are well known for their ability to grow in low light conditions. In your aquarium you should aim for 2-4 watts per gallon for around 8 hours a day. 2 watts is on the low side for light, but it is enough for this plant and will also help to limit algae growth.

However, Hornwort will grow at their best in moderate light conditions (3 watts per gallon). A full spectrum light is not needed but it will help tremendously if you want faster growth.

How To Plant

Hornwort Close Up

You can either float or plant Hornwort. Keeping this plant floating is the preferred option for most people – this is also how it grows in the wild. Just make sure that the Hornwort stays fully submerged. Keeping it out of the water will cause it to quickly dry up and wither away.

Place it where it will not impede the flow or function of aquarium pumps or filter intakes. You can use suction cups attached to the aquarium, then tie fishing line around the suction cups and the Hornwort to hold it in place. To plant them you will need to weigh down a section of the plant with a lead weight and place it on the substrate.

You may find success in placing the lead weights between branches. Although they can grow a rhizoid that can anchor the Hornwort in muddy substrates, it is best to avoid planting it directly in the substrate like you would other plants. Planting it in substrate can cause Hornwort to rot.

Maintenance and Trimming

Caring for Hornwort is fairly straightforward and easy. The largest task will be trimming and pruning them. To trim them you have a few options. You can either trim the side sprouts or trim the end of the main branch.

Choosing what to trim will impact how your Hornwort grows. If you trim from the main stem then it will result in more side growths of the Hornwort. Over time, this will create a plant that branches out instead of consolidating into long growths. Whereas if you cut the side growths the plants will continue to grow straight out and become very long.

Expect Hornwort to grow at least 1 inch per week. This growth rate can grow even faster with high amounts of nutrients and a suitable light source. After you have trimmed your Hornwort you you will need to manage water parameters. First you will need to keep the usual temperature, pH, and waste products in check.

Water changes every fortnight are also essential. Finally, when they shed you should remove the decaying plant matter from your tank.

Placement and Floating

Hornwort can be placed as either a planted or floating. Each placement has certain benefits.

When they are planted they can be used as a background or midground plant due to their size. In this position it can be used by skittish fish, breeding fish, or fry as shelter. The leaves of Hornwort allow fish to hide, as well as serving as nice anchors for egg spawning fish.

You can also float them to create a dense mat. This helps to make shaded areas in your tank which can help shy or low light fish to escape the light.

Fish that stay in the top water column of your tank also interact with these surface plants, weaving between the stems and leaves. If you decide to float them then you will have to take to tie it down and make sure it does not move to new locations in your tank.

Even if you do not have a specific placement in mind, it is very versatile. It can improve water conditions and also aid in oxygen production with photosynthesis.

Hornwort Propagation

Hornwort is very easy to propagate. All you will need to do is avoid trimming Hornwort for a few weeks. Then you will have as much hornwort as you need. You can simply take the cuttings. To make sure new growths do not die off or rot, make sure they are placed away from high flow areas of the tank (like directly below filter outflows) and avoid planting it. It is best to keep it free floating.

If you need to speed up the growth of your Hornwort then you can increase the light intensity and apply plant fertilizer. You can also strategically cut off new growths to allow more ends of the plant to grow at once.

Common Problems

Rapid Growth: Sometimes, too much of a good thing can be harmful. Too much Hornwort in your tank can create prevent other plants from growing. There are ways to limit growth, such as limiting light or nutrients, but the best way to prevent your tank from being overrun is to regularly prune them.

Needle Shedding: If your new Hornwort starts to shed then do not worry, this is perfectly normal. A plant shedding their leaves is indicative of rapid changes in water parameters – plants have to acclimate to new environments just like fish. In a few weeks they will start to grow normally. They do also shed leaves when they are not getting enough light, so watch out for this too!

Damaging Fins: They have thin, rigid, and pointy leaves. This combination can spell disaster for the fins of Fancy Guppies, Beta Fish, or any other fish with long flowing fins. If you keep fish with long flowing fins then you should consider other plants instead such as Anacharis.

Pest Snails: Because Hornworts have a lot of surface area, they can sometimes come with pests when you buy them. The snails that do inhabit them (typically ramshorns snails and bladder snails) are relatively harmless, but they can be annoying for some. So you need to quarantine your plant first before adding them to your tank.

In Conclusion

Hornwort is a great introductory plant for any beginner fish keeper. This plant improves the quality of life for your fish by removing waste products, providing oxygen, and giving shelter.

The problems that do come with the plant are thankfully perfectly manageable – they just need a bit of maintenance on top of your weekly water changes. Overall, the benefits easily outweigh the negatives and they are perfect for practically anyone.

Have you kept Hornwort before? Let us know in the comments section below…