Hornwort Care: The Good, Bad, & Useful

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Hornwort care

Hornwort (Ceratophyllum demersum), or coontail, is a fantastically bushy plant that can be used as a hiding spot for fry or other small fish. It’s incredibly popular in guppy breeding tanks, but works well for just about any tank where fry predation is a concern. It makes a phenomenal site blocker for breeding pairs of cichlids or to break up tension between fish of any species by differentiating territories within the tank.

It’s an exceptionally fast-growing plant capable of growing 5” (12 cm) or more in a single week. Not only does this make it a cheap plant to buy and an easy plant to fill empty tank space, but it also means that it soaks up a ton of nutrients and keeps your water conditions tip top.

It’s great at sucking up ammonia, nitrates, and nitrites, but also providing a ton of oxygen in the process. Since it grows so quickly, it’s also a great option for keeping algae under control in your tank.

Bonus points: hornwort doesn’t need light to grow, so it even grows well in a dark blackwater setup.

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Table of contents

Hornwort species card

Hornwort FAQ

Hornwort Natural Habitat

Hornwort grows from the very top of Canada (by Greenland) and Alaska and all the way to Hawaii and Puerto Rico, covering the entirety of North America (if we’re counting non-continental states.) So it naturally covers a wide range of temperatures and water conditions.

hornwort natural habitat

It’s also considered to be an invasive species in several places because it’s such an adaptable plant.

Hornwort Care

Difficulty: Bulletproof
Size: 2’+ (61 cm+)
Propagation: Side shoots and clippings
Fertilizer: Liquid
Speed of growth: Quickly
Temperature: 63 – 86F (18 – 30C) but it can overwinter too

pH: 5.0 – 8.0 – though likely higher
Hardness: 2 – 25 dKH
Placement: Floating, planted, or weighed down with plant weights
Origin: Southeast Asia
Aquascaping: Background
Availability: Very common

Hornwort makes an ideal pond plant. It grows quickly and absorbs a ton of nutrients, so it controls algae growth phenomenally. Reports say hornwort can grow up to 2’ (61 cm) – but I’ve pulled some out of a pond that was at least 3’ (91 cm.)

Hornwort naturally occurs in cold climates, so you can easily overwinter them by attaching a rock to them and sinking them to deeper water or wrapping them in rockwool. So long as the plant itself doesn’t freeze, it’ll survive and possibly even grow. Even if only part of the plant survives winter, it’ll grow quick enough to repopulate the pond once it stays defrosted.


Hornwort is incredibly adaptable at a variety of temperatures – even below freezing – so long as the plant itself doesn’t freeze – you shouldn’t have any trouble growing it. When it becomes too warm, it will usually start to shed it’s needles and become “stringy” looking.


As lighting goes, hornwort doesn’t even need light to grow and should survive even in the dark. However, it looks greenest and grows the thickest under high lighting, so floating hornwort usually looks the best – but it does fine under any light.  

When lighting is too strong, it’ll start to yellow and become thin and leggy looking. You don’t need special lighting to grow hornwort, but if you want a nice light to have, I have some of my favorites below.

Fertilizers & Substrates

While it does best when left to float in your tank, you can choose to plant it – though there have been reports that it will rot if you plant it. Often it will start to lose it’s “needles” (leaves) at the base of the plant, which can cause it to look “leggy” or “stringy” – at the very least you’ll have plant debris on the bottom of your tank or potentially inside your filter.

Even if you run a bare bottom tank you can keep hornwort either by floating it, weighing it down with a plant weight, or planting it in a pot. Is it possible to have a better plant for a breeding or fry raising setup?

hornwort breeding

I haven’t done any scientific tests, but from my experience, the answer is no.

You likely won’t need any additional fertilizers, but if you find you’re struggling, you can try fertilizers. Because this plant doesn’t have roots, you’re going to want liquid fertilizers, so substrates and root tabs won’t help you with this one.

Common Problems

Like most fast-growing plants, hornwort is not without its problems. Although, bright side: you’re unlikely to ever encounter common plant problems, like algae, temperature, or lighting issues.

Plant Debris

Plant debris aquarium

Plant debris in your tank is a relative problem. If you’re a breeder, your fry and shrimplets will likely enjoy picking off the infusoria and other critters that munch on decomposing plant matter. Similarly, if you have snails, this issue will likely never amount to much. And, so long as you’re not a neat freak, this issue probably won’t bother you.

However, if you don’t fall into one of those three buckets, the mess will probably infuriate you. Additionally, it may cause water quality issues as the plant decomposes and leaches everything it absorbed back into the water. 

Clogging Your Filter

clogged aquarium filter

Funny thing; aquarium filters. They don’t need large particles to clog, just a lot of small particles. Of course, large floating masses of plants will also clog them. 

So as your plant multiplies, sheds, or decomposing plant matter turns into mulm and particulate matter, eventually all of it makes its way to – as you probably guessed – your filter! No matter your filter type; sponge, canister, hang on back, sump, you’ll likely have to up your regular maintenance schedule n your filter.

Ripped Fins

fin and tail rot

Some plants can be rougher than others. While it’s highly unusual for a live plant to cause fins to rip – some tougher or “sharper” (weird word for a plant) plants can certainly cause damage. This is largely dependent on the plant and your water parameters. While some might experience issues, you may not (or visa versa.)

This is usually only an issue with fish that have long, more fragile fins, such as ornamental bettas and some guppies. Occasionally this issue might pop up with more skittish fish that are prone to darting into things. But, again, this depends on your water. So proceed with caution if you fish falls into one o those categories and just monitor how the plant does for the first few months.

Lack Of Nutrients

aquarium plant deficiencies

Fast-growing plants can cause two – er, maybe three – major nutrient issues.

  1. They can choke out other plants by out-competing them for nutrients. Eventually, the plants that can’t compete will slowly die. 
  2. They can soak up so many nutrients that they choke themselves out.
  3. They can out-compete your fish for the same nutrients in the water – especially fry. 

You can fix this issue by doing more water changes to replace nutrients or you can add fertilizers to the water to similarly replace nutrients. Although, both methods will require some tinkering and fine-tuning to get right.

Rapid Growth

fast plant growth problem

While rapid plant growth is a great thing in most cases, it can also become a problem when it comes to regular upkeep on trimming, nutrients, and excess plant disposal. Since fast-growing plants usually present an issue for local waterways and most are considered to be invasive species, taking care to properly dispose of excess is incredibly important.

In addition, it’s quite possible that it can choke out your other plants by out-competing them for nutrients. This can, of course, be remedied by changing the water more frequently, adding more fertilizer to the water, or keeping up on trimming of the faster-growing plants. But, since trimming and disposal also comes with its own issues, this last option is probably the most time-consuming.


Maintaining hornwort is easy – aside from regular trimming and disposal of the unwanted hornwort. Basically, all you have to do is let it sit there. If you have a pond, maintenance becomes much easier so long as you don’t over propagate the plant.

If your plant starts to shed, it might cause some issues with filtration maintenance. This isn’t a problem that’s easily remedied for most people, especially if you don’t have snails to consume dying plant material. It can also make the bottom of your tank messy, as we already discussed, so additional cleanings may need to take place.

hornwort care

Preventing hornwort from getting into local waterways – even if it’s native to where you live – is important for the balance of the local ecosystems. This is particularly true for those who live near wetlands. Since hornwort grows in such abundance, getting rid of it may be a weekly chore for some.

You can bury hornwort (even in your garden for nutrients like you can with duckweed,) add it to your compost heap, or use a bleach soak to kill it before throwing it away (or soak it long enough to dissolve it in bleach.) If that all sounds like too much, you can throw it away in plastic bags to prevent it from getting into local water bodies – although, then you may be introducing more plastic waste into waterways and oceans.


Propagating hornwort is incredibly easy!

You simply cut pieces off and allow those cut portions to grow. Since hornwort grows so quickly, it’s not uncommon to be overrun with it, so unless you have multiple tanks or a way to sell and distribute cut pieces, it’s probably safest not to propagate hornwort (lest you be overrun with it!)

What About Fish?

While hornwort isn’t picky about pH or temperatures, it does best when left floating in low flow environments. It also tends to take up a good deal of space and can damage fins of longer and more fragile-finned fish, like bettas or guppies.

This means you’re going to want to look for fish that like hiding in lots and plant cover. You’ll want to avoid fish that routinely need to reach the surface to breathe, fish who only hang out at the surface, and those who are super active and need tons of swimming space (unless you want more maintenance, that is.)

This still leaves you a good deal of fish to work with. But hornwort really shines in a breeding or fry raising setup for most species of fish. Here are a few ideas for a non-breeding setup, but this is far from a complete list!

Bolivian Ram (Mikrogeophagus altispinosus)

Bolivian Ram

The underrated cousin to the German Blue Ram are often nearly colorless and shy in the store tanks. But provided with the right tank and dither fish, they’ll color up and exhibit fascinating behavior in your home aquarium!

Keep in mind these rams will also become territorial while spawning. However, there are some sparse reports of other tankmates going unnoticed during spawning.

pH: 6.0 – 7.5
dKH: 1 – 10
Temp: 68 – 83 F (20 – 28 C)

Size: 3″ (8 cm)
Temperament: Peaceful
Swimming: Bottom to mid-water

Celestial Pearl Danio (Danio margaritatus)

Celestial Pearl Danio

CPDs or Galaxy Rasbora (although they’re not a rasbora or a danio,) are small shoaling species. When stocking, buy as many as possible,  8 being the minimum I’d personally suggest. There have been reports that they’re hard to transition onto prepared foods, but this may be wild-caught specimens. There are numerous reports that they’ll take finely crushed flakes and micropellets.

pH: 6.5 – 7.5
dKH: 5 – 15
Temp: 69 – 79 F (20 – 26 C)

Size: under 1″ (2.5 cm) 
Temperament: Peaceful, can be shy
Swimming: Mid-water shoaling

Emerald Dwarf Rasboras (Microrasbora erythromicron)

emerald dwarf rasbora

A beautiful shoaling species that needs to be kept in groups of six or more. Even still, they can be a little timid without the right plant coverage. Once settled, they’re an active, gregarious, and beautiful addition to the right aquarium!

pH: 7.0 – 8.0
dKH: 12 – 20
Temp: 68 – 76F (20 – 24C)

Size: .75″ (1 cm)
Temperament: Shy shoaling fish
Swimming: Mid to top

Cherry Shrimp (Neocaridina davidi)

neocaridina shrimp

Neos enjoy munching on decomposing plant matter, grazing on algae, and picking sunken pieces of wood and plants clean. This makes them a perfect addition to a naturalistic tank. They come in a variety of colors including the oh-so-common cherry shrimp!

pH: 6.5 – 8.0
dKH: 8 – 20
Temp: 70 – 79 F (21 – 26 C)

Size: 1.6″ (4 cm)
Temperament: Peaceful
Swimming: Anywhere there’s food to pick, but usually bottom

Sparkling gourami (Trichopsis pumila)

Sparkling gourami

Little known fact about sparkling gouramis; they’re quite social and gregarious creatures! Although they don’t school or shoal, they do enjoy social interactions with their own kind – in fact, most gourami do! – and we suggest a four minimum to make sure they’re comfortable.

pH: 6 – 8
dKH: 5 – 18
Temp: 72 – 81 F (22 – 27 C)

Size: 1.5″ (4 cm)
Temperament: Peaceful, can be aggressive when spawning
Swimming: All water

Ghost Shrimp (Palaemonetes paludosus)

ghost shrimp

Ghost shrimp are usually sold at pet stores as feeders, but they can make great tank inhabitants too! They generally do best in groups of 8 or more and do well with larger fish that won’t eat them. Some very small fish might be eaten by them.

pH: 6.5 – 8.0
dKH: 5 – 10
Temp: 70 – 80 F (22 – 26 C)

Size: 1.5″ (4 cm)
Temperament: Peaceful and active
Swimming: Bottom & structured surfaces

Bristlenose Plecos (Ancistrus sp.)

bristlenose pleco

Most plecos aren’t suited for the average aquarium, some growing up to two feet long – not the bristlenose pleco. They’ll happily munch on algae, green beans, zucchinis, cucumbers, sinking algae wafers, and of course leftovers and fish poo – although leftovers and poo make for a literally shitty diet.

pH: 6.0 – 7.5
dKH: 6 – 10
Temp: 60 – 80 F (15 – 27 C)

Size: 4 – 5″ (10 – 12 cm)
Temperament: Peaceful, can be territorial
Swimming: Everywhere that has structure

Crystal Red Shrimp (Caridina cantonensis)

crystal red shrimp

Crystal red shrimp, not unlike cherry shrimp, come in more colors than just red. They’re a similar size to cherry shrimp and make a great alternative if you’re looking for a little bit more of a challenge. They’re incredibly popular – although more expensive.

pH: 5.8 – 7.4
dKH: 0 – 4
Temp: 62 – 76F (16 – 24C)

Size: 1.25″ (3 cm)
Temperament: Peaceful
Swimming: Surfaces

Corydoras (Corydora sp.)

Panda Cory Catfish

Corydoras are a shoaling species rarely kept appropriately. Some species can be seen in shoals numbering in the thousands in the wild! While this isn’t easily replicated in the home aquaria, most species are happy in groups of six or more like-minded cats to partrol the sand beds with.

Corydoras hasbrosus would be a particularly adorable addition  – although almost any corydora would do well, similarly agreeable in size would be pygmaeus, hastatus, or panda.

pH: 5.5 – 7.0 – species dependent
dKH: 3 – 10
Temp: 72 – 80 F (22 – 26 C) – species dependent

Size: 1 – 3.5″ (2.5 – 9 cm) – species dependent
Temperament: Peaceful, can be boisterous for less active species
Swimming: Bottom (except hastatus) in a shoal of 6 or more

Further Reading & Sources

Further Reading & Resources

Science Direct – Hornwort

Research Gate – Hornworts: An Overlooked Window into Carbon-Concentrating Mechanisms

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