Hornwort Care (Ceratophyllum Demersum)


Last updated on July 3rd, 2022 at 12:22 pm

Hornwort, also known as coontail, ceratophyllum demersum, or hornwort plant, is one of the most common aquarium plants you’ll find at pet stores. It has long green leaves and can grow up to 8-10 inches tall. One of the reasons that people love it so much is because it’s such an easy plant to care for – especially when compared to other, more finicky plants like anubias or java ferns.

Ceratophyllum demersum, commonly known as coontail, or horned pondweed, is a species of aquatic plant that’s native to Europe, Asia, and Africa. It has been introduced in other parts of the world and has become an invasive species in several regions, including North America and Australia.

The plant thrives in still or slow-moving freshwater areas such as ponds, lakes, and rivers but will not do well in saltwater environments.

Ceratophyllum demersum is a freshwater plant in North America. It looks somewhat like moss but is not considered to be such. Hornwort does best in low light conditions with very little movement in its water environment; however, it can survive for days out of water due to its ability to photosynthesize through its leaves even when submerged. Although it can survive in extremely low levels of light, most species thrive with moderate lighting.

Origin and descriptions


Ceratophyllum demersum, also known as coontail, is a type of underwater plant that grows in still or slow-moving waters in North America. Native to Europe, Asia, Africa, and Australia, hornwort grows in streams, lakes, ponds, and water gardens year-round. It can survive below freezing temperatures as long as it is kept moist.

When heated, however, this plant will die if exposed to dry air for more than 24 hours. If cold isn’t an issue, hornwort requires minimal maintenance care. There are several varieties of Ceratophyllum demersum; all boast upright growth structures with feathery foliage on top and fuzzy round roots underneath.

Species profile

Coontail or horned pondweed, is native to both Europe and Asia. The plant is named for its hardy rhizomes, which resemble a miniature deer’s antlers. Its main use in aquaria is as a bottom-dwelling plant that can survive without light—though it will grow more quickly with good lighting conditions. It is fairly easy to care for, but some attention must be paid during all stages of development: planting, growing, and harvesting.

Hornwort species

The Hornwort species is a perennial flowering plant. It is a type of horned pondweed that grows in water or wet soil, usually in aquatic habitats. Some refer to it as a submerged vascular plant because it does not have true roots but has root-like structures called rhizoids that are used for nutrient gathering.

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This species ranges in size from about 6 inches to over 3 feet tall when fully grown. Plantlets grow on older stems near nodes close to where leaves join them, forming large clumps which expand by the growth of new shoots with rhizoids attached. Leaves are lanceolate and vary in length from one inch long up to two feet long.

They grow opposite each other with some leaves having horns protruding from their midsections. They do not spread by seeds, so propagation occurs through new shoots formed at stem joints.

Hornwort scientific name

The scientific name of hornwort is Ceratophyllum demersum

Common names

Common names are water stargrass, coontail, coontail plant,  or horned pondweed

Where are hornworts found?


They are primarily found in North America, Europe, and Asia. They thrive in shallow lakes with a large number of nutrients. Hornwort is often found at water’s edge, which makes them susceptible to run-off from pesticides or fertilizers.

This herbaceous plant was originally introduced to lakes as an aquatic ornamental that has since spread throughout North America. In fact, it was given its name by early settlers who thought it resembled cow tails.

Characteristics of hornworts

Ceratophyllum species have quite a few characteristics that set them apart from other aquarium plants.

  • For starters, they’re free-floating plants: They don’t require soil to grow and can even take root in a hard, rocky substrate. This trait is part of what makes them ideal for aquariums with substrates that are mostly solid rock.
  • Ceratophyllum demersum also has very long roots compared to most aquatic plants—an extension of its preference for hard, flat rocks—which means it doesn’t need much room in your tank. Keep in mind that hornworts will form roots off of their stems if there isn’t enough vertical space.

5 more common characteristics

  1. Hornworts are a family of submerged freshwater plants, comprised of around 30 genera, with over 200 species.
  2. Most of them are found in Europe, Asia, Africa, and North America.
  3. Many have root-like rhizomes that can provide an anchor for colonies in rapidly flowing water (or even mud).
  4. Some species secrete hydrogen peroxide as a defense mechanism against predators.
  5. Botanists refer to most hornworts by their genus name: Ceratophyllum demersum or Ceratophyllum echinatum. Both are commonly known as hornwort—but some varieties may be referred to specifically by other common names like water stargrass or myriophillum aquaticum.
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How to plant hornwort


It’s easy to grow hornwort. Simply remove your plant from its container, rinse it off, place it in a tank, water it, and place it under fluorescent lighting.

Hornwort is an aquatic plant so be sure to keep it underwater. They thrive when placed in moderate lighting but not intense lighting, so if you plan on using metal halide or high output fluorescent lights, you may need to add additional CO2 in order for your hornwort to thrive.

However, if you place your plants under lower output lightings such as T5HO and compact fluorescents, then supplemental CO2 isn’t required. The pH level of hornwort should range between 6-8 which can be achieved through regular dosing of fertilizers such as iron supplements and potassium-based fertilizers.

As far as nutrients go, both iron and potassium are absolutely essential to help fuel photosynthesis within your plants. In terms of fertilizing hornwort, it is recommended that you fertilize them at least once per week by performing ¼ weekly water changes with iron additives. If you have higher output lighting systems running, consider doubling that amount to ½ weekly water changes with iron additives.

How do hornworts reproduce?

They reproduce asexually. As a result, they rarely change in appearance as they age. They also reproduce by spores, which are hard to control in an aquarium setting because they spread easily to other plants nearby. Hornworts can be grown successfully without propagation, but that requires skill with both trimming and overwatering.

Neither of these skills is easy to master in an aquarium environment. Some aquarists believe that propagating hornworts improves plant health, but if you’re using artificial lighting and CO2 enrichment it may not matter if your hornwort reproduces naturally or via tissue culture; either way, it gets plenty of light and nutrients.

Hornwort care


Ceratophyllum demersum is a freshwater plant that will thrive in most aquariums. This plant is native to Europe, Asia, Africa, and Australia. It has been introduced to North America and some Pacific islands.

Hornwort is commonly used in freshwater aquariums because it can tolerate a wide range of water conditions. Despite its name, it does not have any relation to plants in the Zygophyllaceae.

Because they prefer moving water, it tends to attach itself to rocks or driftwood. On driftwood or rocks without currents, stems may spread out widely instead of growing upwards towards the light.

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Light requirements

They should be planted in an area that receives moderate to high amounts of light, especially if you want to encourage photosynthesis. Your plant won’t grow or thrive with too little light, and it may even turn brown or die if you don’t give it enough light.

If you want your hornwort to stay healthy, aim for at least six hours of direct sunlight each day. Alternatively, consider a fluorescent bulb designed for aquariums. You can also add artificial lights to a shade-covered tank; however, your plants will need some time every day under natural lighting conditions.

Plants grown under artificial lights alone will rarely survive as well as those grown under natural light conditions.

Water requirement

The plant is considered a low-maintenance plant that only requires watering when dry. However, it grows quickly so supplemental water may be necessary to maintain optimal growth. Also, because it grows quickly, frequent pruning should be carried out if you wish to keep your aquarium tidy.


It does best in temperatures ranging from 18 to 24 degrees Celsius. Temperatures exceeding 30 degrees Celsius can be fatal to hornwort. An ideal temperature range is 22 degrees. Anytime your water temperature rises over 27 degrees, you should hold off adding any new plants until it drops back into an acceptable range.

This will ensure that they survive their first couple of weeks in your aquarium and give them a better chance at establishing themselves within your setup.


It prefers a high level of humidity. You’ll need to keep it consistently moist, with little to no dryness. The best way to accomplish proper humidity is through regular watering, not misting or fogging. Allow your plants to almost dry out between waterings, but be careful—if you allow them to wilt excessively, they can die.

This plant has medium-light needs; too much or too little light will lead to problems.

Perfect humidity ranges are between 50%–80%. You can maintain higher or lower levels of humidity, but you’ll need to keep an eye on your plants; they may dry out if you aren’t careful.

Can hornwort grow floating?

Hornwort is an emersed aquatic plant, meaning it must be rooted in mud or soil to thrive. While it can grow floating on its own roots, these waterlogged conditions may lead to root rot. For most aquarists, replanting them in submerged soil is a better option. After planting hornwort in your tank’s substrate, simply cover it with 1 to 2 inches of additional gravel or sand for adequate support.

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Is hornwort good for ponds?

Yes. Hornwort is a type of algae that can be found in freshwater or saltwater environments. Hornwort is most often used as an aquatic plant in aquariums because it grows quickly, but it also makes for great pond plants. If you’re wondering if hornwort is good for ponds, then you should know that they are easy to grow and keep clean with regular pruning.

Why is my hornwort turning brown?

The most common reason your plant is turning brown or yellow is from over-fertilization. Over-fertilizing can cause algae to bloom in your aquarium which, if left untreated, will quickly kill off your plant. The fastest way to fix an algae bloom is by removing as much of it as possible. Usually vacuuming your substrate will do enough damage to prevent more growth.

How do you prune a hornwort?

They are perennials, so they will bloom every year if you allow them to live long enough. However, they require plenty of water as a part of their growth cycle. If your hornwort plants aren’t blooming as expected, there could be something inhibiting their growth.

Most of them are either pruned or removed during winter, but you can also prune them in fall or early spring when it’s easier to reach their tops without dying from cold weather exposure.

Is hornwort good for goldfish?

Yes. Ceratophyllum demersum is one of many plants you can use to feed your fish. It has several benefits over other plants when it comes to feeding goldfish. Hornwort is relatively easy to grow in aquariums, due in part to its ability to adapt to varying water conditions.

However, before adding this plant to your tank, you should research its growth habits thoroughly so that you know how it will respond if conditions change dramatically.