The short answer
Hornwort has no true roots (Rutgers Extension, a university service). Aquarium Co-Op, a retailer, says it “grows best as a floating plant”. Buce Plant, a plant retailer, says to anchor stem bases “loosely to hardscape” with weights or suction cups. Tropica, a plant grower, calls planting it in the bottom “possible”; Co-Op says the attached end “tends to rot away”.
Hornwort is Ceratophyllum demersum (Tropica, Co-Op), also called coontail. These steps are for freshwater tanks. See also our beginner plants guide and our java fern, java moss, anubias and Amazon sword guides.
What you need
- The hornwort. Buce Plant, of hornwort that arrives as its lead bunch: “Remove lead weight or rubber bands gently from the stem bases upon arrival.”
- For anchoring: plant weights or suction cups, which Buce Plant names without saying what its weights are made of. On a java fern guide Buce, which sells its own plant weights, says: “Although people commonly refer to these weights as “lead weights” in this hobby, our plant weights don’t actually contain lead.” Check what any weight is made of (our advice).
- Or a substrate; our planted substrate roundup compares soils, gravels and laterite.
Planting method: float it or anchor it
Unplug, then float it
Fluval, an aquarium equipment maker, in its AquaClear filter manual: “Always unplug or disconnect all appliances in the aquarium from electricity supply before placing hands in water, before putting on or taking off parts and while the equipment is being installed, maintained or handled.” Buce Plant: “To keep Hornwort floating, simply place stems directly onto the water surface where they will freely drift and expand under light.” Tropica’s planting guide, under “Floating plants (Limnobium, Ceratophyllum…)”: “You can cut the very long roots and Ceratophyllum can be divided into small pieces. The plants are placed on the surface. Note the shading effect they have further down in the aquarium.” Our reading: the “very long roots” clause is for Limnobium, since Tropica says Ceratophyllum has “no roots as such”. Plug every appliance you unplugged back in once your hands are out.
Or anchor it, knowing the anchored end may rot
Unplug every appliance in the tank first. Buce Plant: “To anchor Hornwort submerged, secure stem bases loosely to hardscape using plant weights or suction cups; avoid burying stem bases deep in dense substrate, as buried portions will decay.” Tropica: “Ceratophyllum has no roots as such, but it is nevertheless possible to plant it in the bottom of an aquarium”. Co-Op: “Some people like to plant it into the substrate or attach it to hardscape, but because it never grows proper roots, the attached end tends to rot away.” Plug every appliance you unplugged back in once your hands are out.
Light need and growth rate, by source
| Source | Light need | Growth rate |
|---|---|---|
| Tropica | Low | Not given |
| Co-Op | “low to high light” | “can easily grow 1-4 inches (3-10 cm) per week” (“With enough light and nutrients”) |
| Buce Plant | Medium to High (Adaptable to Low Light) | Moderate to Fast |
Each source rates on its own scale (Tropica’s is relative to 0.5 W/L; the others give no unit), so ratings are shown as written. Our planted aquarium light roundup compares lights by tank length.
Plant care and troubleshooting
Trim it if it grows out of control
Unplug every appliance in the tank first. Co-Op: “Make sure to prune back your hornwort if it starts growing out of control so that it won’t block out the light if you have other plants or limit gas exchange at the surface if you’re keeping fish.” Buce Plant: “Prune oversized or sprawling stems by simply cutting along any stem node with sharp aquatic scissors, and allow trimmings to float to propagate new plants.” Surplus trimmings are not for outdoor waters: Rutgers warns that coontail “can reproduce from small fragments left behind”; see the disposal section below. Plug every appliance you unplugged back in once your hands are out. Our oxygen guide covers surface gas exchange.
Check the causes if needles shed
Co-Op: “Hornwort sheds needles anytime there’s a major change in water parameters or it’s kept in an unfavorable environment, such as strong currents, not enough light (especially at the base of planted stems), lack of nutrients, or dosing of certain chemicals like liquid carbon.” Its advice: “Don’t throw away the whole plant, but instead wait for it to recover and it will quickly begin growing new leaves and shoots. Also, make sure to gravel vacuum the fallen leaves to prevent excess nutrients from building up in the aquarium.” Buce Plant says shedding “typically happens” with sudden changes in water parameters, “extreme temperature swings” or a new environment. Co-Op: “Hornwort tends to prefer gentle flow, so make sure the needles don’t accidentally get sucked up by your filter intake.” Unplug every appliance in the tank before you vacuum, and plug every appliance you unplugged back in once your hands are out. If it keeps declining, see why aquarium plants die.
Feed only if needed, by the label
Co-Op: “In addition, the fast growth rate means it will quickly drain your aquarium of all nutrients, so you may need to regularly dose Easy Green liquid fertilizer in the water column to ensure that the other plants get enough to eat.” Easy Green is Co-Op’s own fertilizer, and the line gives no amount or schedule beyond “regularly”; follow your fertilizer’s label. Our plant fertilizer roundup compares what each maker says its fertilizer supplies; our fertilizing schedule guide compares makers’ schedules. If fish look unwell after a dosing change, test the water and contact an aquatic veterinarian.
Do not release hornwort or its trimmings
Rutgers, in a fact sheet on New Jersey waterways, calls coontail native to “the entire United States and most of Canada”, but also “a competitive plant that can develop dense subsurface mats in high nutrient waters and displace or out-compete other native vegetation.” The Aquatic Nuisance Species Task Force, a Fish and Wildlife Service program, wrote its guidelines for classrooms and does not name hornwort; our reading is that they apply to an unwanted aquarium plant. They list: “Give unwanted plants and animals to another school or classroom, environmental learning center, aquarium, zoo and where possible return them to the pet store or supplier.” Then: “Dispose of unwanted plants in a sealed plastic bag in the trash. These materials should not be composted because their seeds and other plant parts may spread.” They note that “releases are illegal in most states”, and add: “To find out which species are regulated in each state/province visit www.takeAIM.org”. More setup guides are in our Tank Setup & Care section.
Ready to buy?
Our plant fertilizer roundup compares nine fertilizers, and our Substrate, Plants & Decor section gathers plants, substrates and planted-tank gear.
Frequently Asked Questions
Q. Does hornwort need CO2?
Co-Op: it “does not require carbon dioxide (CO2) injection”. Buce Plant: “Not Required”. Tropica rates its need “Low” on its own scale.
Q. How do I make hornwort grow faster?
Co-Op says it “grows best as a floating plant, where it has greater access to light and carbon dioxide from the air.”
Q. Is hornwort good for an aquarium?
Co-Op: “Fast-growing plants like hornwort are good at “cleaning” aquarium water because they consume waste compounds from the water”. Rutgers, of ponds: it “may help to improve pond water clarity.”
Q. Can hornwort grow from seeds?
Rutgers, on wild coontail: “Reproduction is either by seed or by vegetative growth of plant fragments.”
Sources (6)
- Tropica (grower): Ceratophyllum demersum, Planting
- Aquarium Co-Op (retailer), Hornwort care
- Buce Plant (retailer): Hornwort, Java fern care guide
- Rutgers Cooperative Extension (university), Coontail
- Aquatic Nuisance Species Task Force (FWS program), Classroom guidelines
- Fluval (maker), AquaClear manual
