You’re busy and excited, planning your new aquarium when you decide it needs plants!
You could get the fake plastic stuff, but you recognize your fish would enjoy and benefit more from real flora, plus it’ll look so much nicer!
So, you pop over to the local fish store, where you’ve been spending a lot of time ogling everything anyway, and ask what that green fern-like stuff is in the aquarium? It’s so pretty!
And you discover it’s hornwort!
While the name may not sound so pretty, it’s a beautiful plant that can be easily added to your aquarium.
As hornwort is pretty, inexpensive, and easy to care for, there’s a good chance you’ll go home with some. It’s also compatible with many fish, so it’s great for just about any aquarium.
In this article, we’re going to help you out with the basics of hornwort care. We start with a summarized plant profile, move onto care and propagation, and end with some interesting facts and background information about your new aquarium plant!
Contents - Click to Jump to Section
Quick Overview and Statistics
Just to help you get a quick idea of what hornwort is all about, we have put together a handy table. Then we will explain what it all means.
|Common name(s):||Hornwort, coontail|
|Scientific Name(s):||Ceratophyllum demursum|
|Origin:||North America, +1.6-51 inches of water-depth range, quiet streams, marshes, ponds, still lakes, ditches, prefers clear water with a usual substrate of mud, sand, and rocks.|
|Maximum Size:||Close to 10 inches high in the wild, usually only about two inches in a tank. Forms large beds of plants in the wild. Expands in the tank to form a bush-like plant.|
|Growth Rate:||Rapid growth that requires constant pruning.|
|Water Conditions:||Freshwater, 59–86° F, KH 5–15, pH 6.0–7.5.|
|Minimum Tank Size:||20 gallons|
|Supplements:||CO2 fertilization, high-quality aquarium fertilizer|
|Propagation:||Seeds and side shoots.|
|Tank mates / Compatibility:||Depletes nutrients quickly if kept with other plants. Blue-green algae inhibitor. Compatible with all fish, great for baby fish, as it keeps the adult fish away from them.|
There are two common plants described as hornwort. The one we use in our aquariums is a North American native. It’s uncertain how it was discovered, as it grows so plentifully everywhere across the continent that it’s actually considered a weed. Another common name for it is coontail.
Hornwort (Ceratophyllum demursum L.) is an extremely popular perennial aquatic plant. It has long stems, with many needle-like leaves grouped in whorls along the stem.
As it loves fresh to brackish water ponds, marshes, still lakes, streams, ditches and elsewhere, some enterprising person likely thought it would be great for aquariums. And it is.
Its preferred substrate of mud, sand, and rocks, which is common in its native environments, is relatively easy to reproduce in an aquarium, making it ideal for this purpose.
There is debate surrounding whether it’s a true allelopath or just shows those tendencies. It inhibits the growth of algae, which is good. It also tends to suck in any available nutrients and grows rapidly as a result. This means if you put other plants with it, you’ll need to supplement your tank with extra nutrients.
What Does Hornwort Look Like?
It’s bright green with stems that can grow as long as ten feet high in the wild, but fortunately, they shouldn’t grow longer than a few inches in your aquarium.
There are many, usually around 6–8, densely crowded, needle-like leaves arranged in whorls around the relatively thin stems, which are about .07 inches in diameter.
Hornwort reproduces by creating unisexual flowers. What this means is male and female flowers occur on the same plant, and interact to ultimately create fruit. It generally flowers July through September.
The flowers are very small. The reddish petals are found in bunches of about eight to 12 at a time, and they occur in the base of any given whorl.
They create an achene fruit (a common example of an achene is a sunflower seed), which is about 0.16 to 0.24 inches and shaped like an oval, with one to two basal spines. This fruit breaks off and sinks into the substrate in the autumn, and forms new plants in the spring.
Because it is free-floating, rootless, and naturally anchors itself in the substrate, the most common method to propagate it in aquariums is simply to prune the shoots and plant them. It breaks apart naturally in the wild and propagates itself this way too.
There are many species and subspecies of hornwort in the wild, but generally, only C. demursum is used for aquariums.
This time-lapse video of hornwort growing shows just how beautiful this plant is:
Placement in a Tank
Because it is a lovely bright green stem plant, it makes for an excellent background plant. It grows very quickly and will grow up to 2 inches high in most cases, but can reach as much as 10 inches – though very, very rarely. So it will make an excellent frame for your fish and coral.
It isn’t suitable for a carpet plant unless you want to fill your tank with it. Since it grows quickly and to a reasonable height, you don’t want it as a midground or foreground feature—it will block the view of the fish and coral.
How Hornwort Can Benefit Your Aquarium
Placing it into your aquarium adds so much more than aesthetics. While it’s lovely, feathery appearance accents your aquarium’s look, check out some of the other amazing benefits it can bring.
It secretes substances that inhibit the growth of algae, thereby creating a welcoming spawning habitat for fish and invertebrates—not to mention, it’s compatible with all fish.
It’s particularly great for small fish, as it can be a food source and a hiding place, protecting them from larger fish.
Hornwort helps to clarify water and has oxygenating qualities. It’s also highly adaptable to different water types and can tolerate a wide range of temperatures.
As the it’s natural habitat is everywhere across the USA, and it’s actually considered to be an invasive species to a certain degree, it is naturally adapted to just about any situation. It is therefore very easy to care for and a great plant for beginners.
It naturally occurs, as we have said, in ponds, lakes, marshes, ditches, and streams. It is, however, a freshwater plant only.
Let’s see how to setup your aquarium for optimum hornwort care at home.
Minimum Tank Size
Hornwort grows to about two inches in tank environments, which isn’t so high, so means it is suited to all shapes of aquariums. However, the smallest you should go to is about 20 gallons.
Water Type and Parameters
This plant is only suitable for freshwater tanks. It can handle a temperature range of 59 to 86 degrees Fahrenheit, which is a pretty wide range.
An important aspect to look at in aquarium water is the KH level of the water. KH in aquarium keeping is the measurement of carbonates and bicarbonates in the water. The scientific standard is 1 dH = 17.8 ppm CaCO3. In general, you do not want to let your level drop below 4.5 dH.
The KH level is important, as the carbonate and bicarbonate levels act as a buffer to stabilize that all-important pH.
Hornwort has a wide tolerance of KH levels, 5 to 15 dH. It will, therefore, do pretty well regardless of the contents of the water.
It similarly shows a wide tolerance of pH levels as well, surviving handily in a range of 6.0 to 7.5 pH. Since 6.0 is acidic and 7.5 is quite alkaline, this is the chemical equivalent of being able to survive just as well on snow-capped peaks as it can in a rainforest!
If your water levels don’t fall between 6.0 and 7.5 pH, you will have much more trouble than just keeping your hornwort alive, you will not be able to keep much of anything alive. So it’s therefore great for just about any tank!
Moderate lighting will more than suffice for. Moderate means mid-range—not particularly bright or dark. Species that do well with moderate lighting generally have the most flexibility.
In nature, hornwort likes mud, sand, and rocky materials. This substrate also naturally contains moderate to high levels of nutrients.
To reproduce this in an aquarium, use mud, muddy gravel, or sandy mud. Because it grows quickly and depletes nutrients fast, you may need to supplement with a high-quality aquarium fertilizer.
There is some debate about whether CO2 fertilization is needed, with some recommending it, but most sources not.
So you probably have the picture by now that hornwort will happily suck up all the nutrients available to it in a tank and grow like crazy. It will do this to the point that it’s easy to propagate; just cut off a shoot and plant in the substrate.
You’ve probably also figured out that it’s highly adaptable to any environment it finds itself in, which is why it’s considered a weed in the wild!
In the wild, it has been known to form beds which displace other plants, so yes, it will take over your tank if you let it.
Hornwort will naturally grow best in conditions ideal for it; however, all conditions appear to be ideal, so what you’ll likely have to deal with is a fast-growing plant that you have to keep control of. You will probably have to prune it—a lot.
As previously mentioned, hornwort care and maintenance is incredibly easy. However, there are some things to keep in mind if you want the healthiest and lushest looking plants.
It needs to be pruned frequently to keep it at appropriate levels in your tank and not to let it take over. Additionally, you may wish to plan for how to control the needle breakage and debris in your tank. Generally, snails, shrimp, pleco, and other scavengers will take care of this for you.
It may or may not need CO2 fertilization. Some report yes, many no. But it will likely need a fertilizer, as it sucks up nutrients—especially if other plants are in the tank with it.
Since it naturally repels algae and will decrease the amount of tank algae just by being there, there is no special treatment needed.
Keeping the tank healthy for your fish will keep it healthy for hornwort too. If you have tank conditions unfriendly to this plant, it’s likely that your fish will be in trouble as well.
Although you could certainly buy hornwort online if you needed to, it is so plentifully available that the best place to buy it is your local aquarium supply store.
They are generally available in six- to eight-inch-long bunches and are relatively inexpensive. Although we’ve seen them listed for more, if you’re paying more than three to four dollars for your bunch, you are paying too much.
One seller listed a bunch for fifteen dollars! Reputable aquarium supply stores carry them for four dollars or less, mostly. We would recommend avoiding sellers that do not specialize in aquarium supplies, as prices were higher in these places.
Pick your hornwort out like you would veggies at the supermarket. Does it look fresh and healthy? Is it bright green? Does it look wilted? Pick a good, healthy bunch, and you will be just fine.
How to Plant It
There isn’t much of anything to do except break off anything that looks dead, and it should be ready to go. Simply add it to your tank. It really is that easy!
How to Prepare Your Tank
To prepare your aquarium for the plant, again you will need a mud, sandy mud, or muddy gravel substrate of your choice. Apply the substrate and then fill with water, using whatever materials and methods you prefer.
How to Actually Plant It
It is so amazingly versatile, there is a lot you can do with it. The basic steps include placing it in the tank and burying one end anywhere in the substrate until it is anchored. The plant will take over from there!
Alternatively, you do not have to plant it at all; you can just throw it in your tank and let it float.
This guy got creative and made himself a hornwort tree. Again, use your imagination!
Tankmates and Compatibility
It will grow with basically any other plant out there. The thing to remember is that it sucks in nutrients, so if you are putting other plants in with it, you absolutely will need fertilizer!
What Plants to Avoid
The only thing to worry about here is over-planting your tank. If you put in a lot of hornwort, and say, a carpet plant too, you would have a lot of flora in your tank and much less room for fish.
Along these lines, avoid any plants that also highly consume nutrients. You will have your plants sucking up all the nutrients; have to fertilize a lot, and the whole environment might suffer as a result.
Best Fish Tankmates
It is a good tankmate for pretty much all fish, but it’s best for live-bearing fish, like mollies and guppies. The fry hide in the thicket environment that the plant creates.
Gouramis and angelfish will eat it, so this is a good additional food source for them.
You can control the debris from hornwort with snails, shrimp, pleco and other scavengers. One user reported proliferation of snails in his tank after he added the plant, so bear this in mind!
Fish to Avoid
There aren’t really any fish that don’t work with hornwort. However, we would consider avoiding any fish that grow very large, as they might find the environment restrictive. These types of fish would require a large, clear tank anyway.
Propagation and Reproduction
In the wild and in tanks, it mostly reproduces and propagates by side shoots, which break off and then form new plants. They also generate male and female flowers, which produce fruit then seeds, and these will fall into the substrate and produce new plants.
The propagation from side shoots is so common, the second method isn’t really needed. In the wild, they spread so effectively via side shoots breaking off that they are considered a weed. It’ss made more than one invasive species list in the world.
The very fastest way to propagate hornwort at home is simply to take a piece you cut off and plant it or float it.
- Hornwort is so biodiverse it was used in a study about flame retardant accumulation in plants.
- It is on several invasive species lists. It originated in North America, but largely through the aquarium trade, has propagated internationally.
- It can be used as animal feed, although this isn’t common.
- It is sometimes used to mix in manure/mulches.
- Vast underwater beds of hornwort have negatively impacted hydroelectric power stations in New Zealand.
Hornwort is a great, easy freshwater aquarium plant, suitable for all fishkeepers—beginners especially. It’s good as a background plant, but because you can use it as a floater or plant it, the possibilities are endless. It is relatively indestructible and an excellent companion to most fish and plants.
At a minimum required tank size of 20 gallons, it will fit all but very small tanks. It isn’t picky about its environment. Just provide moderate light and nutrition through fertilizer supplements, and watch it grow!
We hope you have enjoyed this article. Let us know how we did in the comments. Feel free to ask a question or share your own hornwort stories! Let’s help each other! We will reply to every comment.
Happy fish keeping!