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Hornwort (Anthocerotophyta): The Ultimate Care & Maintenance Guide

Hornwort is a stem plant appreciated for its easy care, decorative growth pattern and its fast growth. This species is perfect if you’d like to add a kick of green to your aquarium while still keeping things low-tech. No added Co2 necessary, your fish will love it and it even thrives in coldwater tanks. What more could we ask for in a plant?


Quick Hornwort Care Guide

Common name(s) Hornwort, coontail
Scientific name Ceratophyllum demersum
Difficulty Easy
Light level Medium
Growth rate Fast
Placement Background
Temperature 60-86 °F / 15-30 °C
pH 6-7.5

What is Hornwort?

Hornwort is a fully aquatic green stem plant also referred to as coontail. It derives this name from its growth pattern. Small, needle- or hairlike leaves grow on tall stems, giving the plant the appearance of a furry tail. There are many species out there in the genus Ceratophyllum, but the one you’ll most likely find in your local aquarium store is Ceratophyllum demersum.

In the wild, you’ll find hornwort naturally in various temperate regions including many countries in Europe, Northern Asia and North America. Additionally, it’s an invasive species in many places, as it can grow pretty much anywhere it ends up. Many sources note that you’ll find Ceratophyllum species on almost every continent! As this wide natural (and unnatural) range suggests this plant is pretty hardy, which is what has made it such a popular choice for both ponds and fish tanks.

One of the best things about hornwort is that it’s very versatile. The plant doesn’t naturally send roots into the soil but it does anchor in the substrate if the need arises. This means you can leave it floating to provide your fish with some shade and shelter or grow it as a background plant for interesting extra texture in your aquascape. The plant’s stems divide as it grows taller, making for a bushy appearance that really brightens up your tank and can be reminiscent of a Christmas tree. If left untouched the stems will eventually reach the water surface. Healthy plants might even produce little flowers.

If all this has made you excited to grow hornwort, keep reading! We’ll discuss everything you need to know to keep this aquarium plant alive and help it thrive, starting with having a look at the way it grows in the wild.

Hornwort Natural Habitat

As mentioned above, hornwort can naturally be found on almost all continents (with the exception of Antarctica). With some accidental human interference it has become even more widely spread over recent years, as it’s now an invasive species in many places. This can be a significant problem because the species grows so dense that it can actually block waterways, choke out native plants and cause all sorts of other issues.

The reason hornwort has been spotted as far north as Norway is that it’s very tolerant to pretty much anything nature can throw at it. It thrives in a very wide range of water values and temperatures. Even if things do get pretty chilly, like in Norway, that’s not always a concern for this species. It can form turions, which are basically small modified bits that some floating plants toss to the bottom of the lake or pond when things start getting cold.

The turion stays at the bottom, which hopefully doesn’t freeze over, and re-sprouts when the water starts warming. Voilà: the hornwort has survived winter.

Hornwort Requirements

Although the invasive nature of Ceratophyllum is definitely a concern, it also tells us a lot about what this plant is like. If it’s a weed in the wild, we’ll love it for our aquariums! After all, for those that are purposely growing greenery, rapid, dense growth and tolerance to a very wide range of water values and temperatures are actually rather good things.

All of the aforementioned characteristics are what made hornwort so popular among aquarists (and pond keepers). Just following a few basic guidelines should be more than enough to keep it alive and thriving, even if you’re a beginner.

Hornwort Lighting

Hornwort naturally floats at the water surface of lakes and marshes, where it can soak up a good bit of light. In the aquarium it’s a good idea to go with about a medium light intensity. In clearer terms for those who are not acquainted with the ins and outs of aquascape lighting yet: that means the stock light on a cheap aquarium kit might not be enough, but you don’t need an expensive and high tech lighting system either. Too little light and your hornwort might not grow properly and turn very leggy. On the other hand, if you supply too much light this plant can also suffer, so find the middle ground for the best growth.

Hornwort Temperatures

One of the best aspects of hornwort is the plant’s tolerance to a very wide range of water temperatures. It can handle temps anywhere between 60-86 °F (15-30 °C). High temperatures are more of a problem than low ones, but generally you shouldn’t expect any temp related issues with this species. In fact, temperatures even lower than what’s mentioned here are likely not too much of an issue, especially for shorter periods of time.

Its tolerance to low temperatures has made hornwort a favorite among aquarists with unheated aquariums. Definitely a plant to consider if you’re thinking about ditching the heater and going for a subtropical set-up!

Hornwort Growth

Another reason Anthocerotophyta is so widely appreciated is that it’s a very quick grower. This characteristic doesn’t just come in handy in terms of aesthetics but also has another advantage….

The species guzzles nutrients, including compounds like nitrates and phosphates that can be harmful to our fish in higher concentrations.If you’re only growing hornwort in a normally stocked aquarium you likely won’t have to supply any extra nutrients nor add Co2.

If you’re also looking to grow other plants and/or if your aquarium is very lightly stocked with only a few fish or inverts, keep an eye on the greenery. As briefly mentioned in the section on hornwort’s natural habitat, this plant can actually choke out other species simply because it consumes so many nutrients.

If you feel like your plants could look a little better, you might be best off investing in at least a liquid plant food to supply some extra nutrients. These products can be found at every aquarium store, are generally not too expensive and might give your plants exactly the boost they need.

Water Values

Anthocerotophyta didn’t manage to conquer almost every continent on the planet by being sensitive and picky about water values. In fact, specific water composition is probably the least of your concerns when it comes to growing this hardy species. A pH between 6 and 7.5 and moderate hardness is usually recommended but honestly, with a bunch of hornwort being so affordable you can always try it to see if it thrives in your tank even if your water values are out of this range.

Planting Hornwort

As we’ve discussed, hornwort is naturally a floating plant. This being said, it does possess the ability to grow lodged in substrate using modified anchoring stems to keep it in place. This means that in the aquarium you can go whichever route you like with hornwort.

The Floating Approach

If you’d like to leave your hornwort floating, there is literally nothing you need to do aside from tossing it into the tank. Do keep in mind that with its fast growth this species can quickly take over the entire surface of your tank and will block out almost all of the light eventually. Unless you remove stems regularly any plants below it that don’t do well in low-light environments might suffer in this relative darkness.

The Fixed Approach

If you want to plant hornwort keep in mind that it can be a little bit of a challenge to keep it in the substrate, especially if the plant hasn’t developed its “anchors” yet. At the same time you can’t just shove the stems into the sand or gravel; you’ll have to do so carefully. Damaged stems often won’t grow very well any more, nor do stems that are buried too deeply.

One solution many aquarists use for stem plants are suction cups. It might not look the prettiest at first, but you can use suction cups meant for aquarium heaters to keep your hornwort in place without damaging the stems. A great option if you’re having trouble growing the plant in the substrate and with this plant’s fast growth it won’t take long before you can’t see the suction cups any more.

Hornwort Care & Maintenance

Although some aquarists experience difficulties getting hornwort to take off, the plant is pretty much indestructible once it does. Whether a lot of maintenance is needed when growing hornwort depends entirely on your goals with the plant. If you’re growing it in a breeding tank or just want as much greenery as possible, it’s probably a good idea to mostly leave the plant alone. If you’re growing it for aesthetics, though, a little more work might be needed.

As mentioned earlier hornwort is a very fast grower that can quickly take over (the surface of) your aquarium. As a result it might deprive other plants of light, causing the more needy species to suffer. Additionally, if you planted the stems of your hornwort in the substrate and the plant subsequently takes off to and populates the entire water surface, its bottom parts can end up looking a bit sparse. This is caused by the fact that the lower leaves won’t receive much light and might shed, leaving half-bare stems.

If this look is not your thing, the best thing you can do is prune your hornwort regularly. Don’t be afraid to grab the aquarium scissors and get snipping! As we’ll discuss later in the section on propagation, cuttings can be used to re-grow the plant. Additionally, pruning forces the plant to create offshoots, making for a denser look.

Using Hornwort in Your Aquarium

The Ceratophyllum genus is very versatile and can be used for many different purposes. We have to mention that most aquarists don’t utilize this species for aquascaping, although it’s definitely not impossible to enhance a planted tank’s looks using hornwort. We’ll describe its various uses below.

Hornwort in Breeding Tanks

Hornwort (along with other bushy stem plants and mosses) is a popular plant among fish breeders. Some fish like to deposit their eggs on fine-leaved plants, which means hornwort is the perfect choice if you’re looking to breed these species.

After the fish are done spawning all you have to do is simply remove the parents (or the hornwort with the eggs attached to it) and voilà, you’ve got the perfect little nursery for the tiny fry to grow in until they’re large enough to venture out on their own. The plant offers cover as well as a buffet of biofilm, which grows abundantly between its textured leaves.

You can also use hornwort if you don’t want to raise baby fish separately but are worried about the parents eating them. Although not all fry will likely make it, this bushy plant offers great protection and really helps them stay in hiding until they can go out into the open without being cannibalized.

Advantages of Hornwort

Apart from its handiness when it comes to fish breeding, Anthocerotophyta has some other advantages. As we’ve discussed, the plant is what some aquarists call a “nitrate buster”. A healthy bunch of such a fast-growing stem plant can really help keep your aquarium healthy and stable by absorbing harmful nitrates from the water.

Contrary to what some like to believe you’ll still have to do regular maintenance and water changes, but at least you know your fish are protected from high nitrates and spikes in other harmful compounds between maintenance sessions.

Aquascaping with Hornwort

If you’re looking to add a pop of green to your aquarium without having to worry about buying extra light or technology, hornwort makes a great choice. As we’ve described earlier this plant is a very quick grower in most tanks. Perfect for that lush jungle look!

Hornwort as a Background Plant

Hornwort grows quite tall and will reach for the water surface if left to grow freely. This means it’ll work best in your aquarium if used as a background plant. The plant’s bushy growth and textured leaves can really spruce up an otherwise boring aquascape if used right.

Hornwort as a Floating plant

Although floating plants are sometimes considered ‘messy’ looking, it all depends on the way they’re used. While floating hornwort might look a little out of place in a regular aquascape it could be fantastic for some biotope aquariums. Floating hornwort, dimmed light, slightly tinted water and plenty of leaf litter on the bottom make for an aquarium that’s both decorative and a place your fish will love.

Hornwort Propagation

As with all stem plants, propagating hornwort is a breeze. In fact, combined with this plant’s quick growth you’ll most likely quickly end up with more stems than you know what to do with!

All you need to do to turn hornwort into more hornwort is divide the stem. For example, you can re-plant pieces that you removed while pruning overly tall pieces. Give the cuttings a few weeks and they’ll continue growing as they normally would. This means it’s not difficult at all to get a real hornwort forest going in your tank, and you’ll likely have plenty more stems to sell, give away or even use as compost.

Common Problems with Hornwort

If you’re having trouble with hornwort, the first thing to ask yourself is whether the plant has been moved recently. Many plants, including this one, don’t appreciate changing conditions. They respond to a move with the dreaded “melt” and, in this case, excessive leaf shedding.

If you did indeed move the plant less than a few weeks ago, give it a little time. Hornwort should be able to adapt to a well balanced aquarium. If it doesn’t then the tips below might be helpful.

Hornwort losing leaves

A mature hornwort stem with side shoots can resemble a Christmas tree. Unfortunately, this plant is also known to shed like one! If you’re seeing some hornwort leaves on your substrate or floating at the water surface on a regular basis, don’t worry. If the plant is starting to look particularly sparse, however, there might be something more going on.

Hornwort turning yellow

There are a few different causes for yellowing hornwort and it can be a challenge to figure out which one you’re dealing with in a specific case. All you can do in order to figure out what is going on is take a good look at the conditions in your aquarium and see if anything is off. A water test can reveal a possible nutrient deficiency; lack of iron in particular is known to cause yellowing. Another common culprit is insufficient lighting. In lower light tanks it might be better to float hornwort than to plant it in the substrate, as more light will reach it this way.

Hornwort “melting”

As with yellowing, it can be difficult to figure out why your plant sometimes just completely melts away in a matter of days (leaving a big mess in the process!). Again, have a close look at your water parameters and don’t forget to consider whether you’ve changed anything in the aquarium right before the melt set in. For example, some aquarists suggest that hornwort is very sensitive to liquid carbon. Also, as mentioned in the introduction of this paragraph, this plant responds particularly badly to change and being moved. In unlucky cases, moving hornwort stems can result in complete and irreversible decay.

Hornwort turning brown

Seeing the tips of your plant turning brown can be pretty worrying – is the new growth not healthy? Don’t worry, it actually is! Healthy hornwort plants exposed to plenty of light can take on a reddish or brownish color. Unless you’re seeing excessive leaf loss or yellowing, keep doing what you were doing.

Buying Hornwort

Hornwort is among the most popular aquatic plants out there and you shouldn’t have much trouble finding it in your local pet- or aquarium store. Because this plant is also popular with pond keepers and sometimes associated with ponds rather than fish tanks, you might need to head over to that section of the store to find it. It’ll often be labeled ‘oxygenating plant’ or something similar.

If you don’t feel like heading out to the aquarium store to get some plants, you can also easily find this species online. There’s plenty of sellers out there and their products are often fresh from the nursery and high-quality. Additionally, they might be cheaper because the seller doesn’t have to maintain a physical store. Plants ship just fine, so there’s no need to worry about death or decay.

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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