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Plants / Stem Plants
Hornwort
Stem Plants · Tough

Hornwort

Ceratophyllum demersum

Has no true roots. Grows very fast and soaks up nitrate, helping to fight algae.

Check your local laws. NZ: Declared an unwanted organism by the Ministry for Primary Industries; regional pest (e.g. Canterbury RPMP exclusion programme): may not be sold, propagated or spread. Never throw it into ponds, rivers or drains.

Needs

Care levelEasy
LightLow
CO₂Not needed
GrowthFast
HeightUp to 80 cm
Temperature10–30 °C
WhereBack of the tank
Feeds throughLeaves, from the water
FamilyCeratophyllaceae
Native toCosmopolitan (native on every continent except Antarctica); introduced in New Zealand, Hawaii, Mauritius and the Cape Provinces of South Africa
Facts checked against sources on 16 Oct 2026. See sources

How to keep it

  • Float or plant
  • Low light is enough (Tropica); medium to high speeds growth
  • Expecting it to stay planted without anchoring

Sources

15 facts checked with sources

  • Scientific namePlants of the World Online (Kew) name search: Ceratophyllum demersum · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • FamilycorrectedPlants of the World Online (Kew) name search: Ceratophyllum demersum · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • Native rangecorrectedTropica: Ceratophyllum demersum (021APOR) · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort · Plants of the World Online (Kew): Ceratophyllum demersum
  • Plant typeFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • LightcorrectedTropica: Ceratophyllum demersum (021APOR) · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • CO₂Tropica: Ceratophyllum demersum (021APOR) · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • GrowthFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • Care levelTropica: Ceratophyllum demersum (021APOR) · Flowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • HeightcorrectedTropica: Ceratophyllum demersum (021APOR)
  • TemperaturecorrectedFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • Where to plantFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • Water or land plantcorrectedFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • AboutFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • Care tipsFlowgrow plant database: Ceratophyllum demersum - Rigid hornwort
  • LawscorrectedEnvironment Canterbury (NZ): Hornwort pest profile

Good with

Animals that leave it alone

GuppyPoecilia reticulata
Easy6 cm22–28 °C
PlatyXiphophorus maculatus
Easy6 cm20–26 °C
Fancy goldfishCarassius auratus
Easy20 cm10–24 °C
Cherry shrimpNeocaridina davidi
Easy3 cm18–28 °C