Hornwort

Ceratophyllum demersum

A rootless plant that simply floats or is tucked into the substrate, and grows so fast it clears the water of the nutrients algae live on. Common in ponds and lakes across the whole world, and one of the first plants for a new aquarium.

Light: low
Difficulty: very easy
Height: 5 – 30 cm (2 – 12 in)
Temperature: 4 – 30 °C (39 – 86 °F)

Native rangeRange on the map

Alabama
Alaska
Albania
Alberta
Algeria
Altay
Amur
Angola
Argentina Northeast
Argentina Northwest
Argentina South
Arizona
Arkansas
Assam
Austria
Azores
Baleares
Baltic States
Bangladesh
Belarus
Belgium
Benin
Bermuda
Bolivia
Borneo
Botswana
Brazil South
British Columbia
Bulgaria
Burkina
Burundi
Buryatiya
California
Cambodia
Cameroon
Canary Is.
Caprivi Strip
Central African Republic
Central European Russia
Chad
Chile Central
China North-Central
China South-Central
China Southeast
Chita
Colombia
Colorado
Congo
Connecticut
Corse
Costa Rica
Cuba
Czechia-Slovakia
DR Congo
Delaware
Denmark
District of Columbia
Dominican Republic
East Aegean Is.
East European Russia
Egypt
El Salvador
Eritrea
Ethiopia
Fiji
Finland
Florida
France
Free State
Gabon
Georgia
Germany
Ghana
Great Britain
Greece
Guatemala
Guinea-Bissau
Haiti
Honduras
Hungary
Idaho
Illinois
Indiana
India
Inner Mongolia
Iowa
Iran
Iraq

Leaf colour: green
Plant type: stem plant
Growth rate: very fast
CO₂ demand: low
Tolerates light: medium – high
Carbonate hardness: 5 – 24 °dKH
Placement: background, spawning plant +2 background, spawning plant, midground, surface
Propagation: fragmentation, cuttings
Grows emersed: no

Appearance

Stiff, needle-thin leaves sit in whorls around a long stem, so the plant looks like a green bottle brush. It has no proper roots at all — nothing holds it to the ground, and in the water it keeps its shape by itself.

Keeping

About as hardy as an aquarium plant gets: it grows in cool water and in warm, in dim light and in bright, without carbon dioxide and without fertiliser. The catch is the speed — it needs cutting back every couple of weeks, and in poor light the lower parts shed their needles and litter the tank.

Placement

Either let it float at the surface or push the stem ends into the substrate along the back wall; it will not root, but it stays where it is put. A floating tangle is a nursery: fry and shrimp hide in it, and many fish spawn straight into it.

Propagation

By itself. The stems break into pieces and each piece grows on, so a single portion turns into a thicket in a month. To speed it up, cut a stem in half and let both parts float.

Water conditions match

The water suits 1017 of 1249 species in the catalogue — these are the ones people look up most often.

Swordtail Guppies Cobra Guppy Blood Red Molly Butterflyfish Red Zebra Cichlid Julii Corydoras Red-finned Parotocinclus Gastromyzon monticola Egg-shaped Goldfish Flame Tetra Gardner's Killifish African Tetra Kenyi Cichlid Cuckoo Catfish Golden Swordtail Hypsolebias picturatus Common Zacco Labeo Bicolor Gambusia Flying barb Gastromyzon scitulus Albino Zebra Danio Geophagus Brokopondo Zebra Mbuna

Will eat this plant

These species damage plants, especially when their diet is short of vegetable food.

Bengal Loach Zebra Loach Burmese Border Loach Emperor Botia Spined Loach Marbled Headstander Pellegrin's Leporinus Leporinus striatus False Black Tetra Common Metynnis Mylossoma duriventre Red Whiptail Catfish Molly sphenops Balloon Molly Lyretail Molly Marble Molly Hi-Fin Platy Hawaii Platy Blue Platy Pintail Platy Black Platy Chocolate Molly Moonlight Gourami Melanotaenia parva

Will uproot it

These species dig through the substrate and pull rooted plants out.

Marble Loach Peacock Eel Forktail Loach Guntea Loach Long-nosed Loach Horseface Loach Pearlscale Black Moor Goldfish Shubunkin Painted Pleco Featherfin Synodontis Reddish Mystus Catfish Blue Acara Aulonocara maylandi Aulonocara multicolor Aulonocara Orchid Geophagus altifrons Geophagus winemilleri Pearlscale Cichlid Pearl Cichlid Redbelly Cichlid Red-spotted Cichlid Chuco godmanni Haplochromis philander Red Chromide Jack Dempsey cichlid

Matching water does not mean the fish will leave the plant alone.

The same plant with a different look: light, water and care are shared with the species.

Ceratophyllum demersum 'Mexiko' ('Rotstängelig')

Other varieties: Ceratophyllum demersum Foxtail

Scientific and other names, conservation status

Other scientific names: Ceratophyllum aquaticum, Ceratophyllum aquaticum demersum, Ceratophyllum asperum, Ceratophyllum cornutum, Ceratophyllum demersum adei, Ceratophyllum demersum tuberculatum, Ceratophyllum demersum apiculatum, Ceratophyllum demersum commune, Ceratophyllum demersum commutatum, Ceratophyllum demersum inflatum, Ceratophyllum demersum notachanthum, Ceratophyllum demersum oxyacanthum, Ceratophyllum demersum pentacanthum, Ceratophyllum demersum platyacanthum, Ceratophyllum demersum strypense, Ceratophyllum demersum tricorne, Ceratophyllum gibbum, Ceratophyllum indicum, Ceratophyllum oxyacanthum, Ceratophyllum submersum apiculatum, Ceratophyllum submersum demersum, Ceratophyllum tricorne, Ceratophyllum tricuspidatum, Ceratophyllum tuberculatum, Ceratophyllum verticillatum, Ceratophyllum vulgare, Ceratophyllum vulgare oxyacanthum, Dichotophyllum demersum
Ceratophyllum demersum: L.
Family: Ceratophyllaceae
Conservation status: LC

Hornwort

Tank conditions

Care and keeping