Hornwort (Ceratophyllum demersum) care guide

Group
Plants
Other names
Hornwort, Coontail, Rigid hornwort, Hornweed
Family
Ceratophyllaceae (hornwort family)
Origin
Almost worldwide on every continent except Antarctica
Water
freshwater
Maximum size
80 cm
Temperature
10–30°C
pH
6–8.5
Hardness
5–25 dGH
Care level
beginner
Lighting
Low light; CO2 not needed

Care

Hornwort, or coontail, is one of the most widespread water plants in the world, found in lakes, ponds and quiet streams that are rich in nutrients. It has no true roots: its stems carry whorls of 6–12 stiff, brittle, forked leaves with small teeth, giving a bottlebrush look. In the wild the stems can reach 1–3 m. In the aquarium it can be left floating, where it makes a dense tangle that shelters newly hatched fry, or weighted or pushed lightly into the substrate in the background. Tropica sells a compact form collected in Bolivia with closely set leaves and side shoots and sturdier stems; it grows 5–30 cm in two months and up to about 80 cm. It is undemanding, with low light and CO2 needs, and suits both coldwater and tropical tanks (summer water in its habitats is about 15–30 °C). It grows quickly, takes up nutrients and releases substances that hold back algae and blue-green "algae", so it is a good plant for new tanks. pH and hardness figures are our estimate, not from the sources. It sheds needles when moved, and drops its leaves if snail treatments are used, but usually regrows within a few weeks. Its fast, dense growth can crowd out other plants, and it is classed as an unwanted weed in New Zealand and Tasmania. Never release this plant or dispose of it in drains or waterways; it is invasive in some countries. Sources: Tropica (tropica.com/en/plants); Wikipedia (en.wikipedia.org/wiki/Ceratophyllumdemersum); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

Simply cut or break off pieces of stem; each piece grows on. Side shoots can be snapped off once long enough. In the wild it also forms winter buds (turions) that sink and sprout in spring, and tiny flowers produce small spiny nuts.

Compatibility and tank mates

Tough and slightly bristly, so it is ignored by most fish, though goldfish nibble it. Excellent for livebearers, killifish and other egg-layers as fry cover, and safe with shrimp and snails. Suits coldwater, pond and tropical tanks.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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