The rough horn leaf is often used as a miracle weapon in the pond to free the water from excess nutrients and algae. It is considered an indispensable aquatic plant for filtering in ponds. In Europe, two species are of particular importance: Ceratophyllum submersum and Ceratophyllum demersum, also called horn leaf. The only difference between the two plants is the arrangement of the leaf whorls. This plant portrait is intended to show what the aquatic plant is really capable of. And: where the horn blade reaches its limits.


  • botanischer Name: Ceratophyllum demersum
  • other names: Rough Hornblatt
  • belongs to the Hornblatt family
  • grows entirely under water
  • Shoots up to 1 m long
  • finely branched leaves
  • usually green or reddish in color
  • forms no roots
  • lives free-swimming or anchored in the ground

living conditions

The rough horn leaf is at home in almost all standing or slow-flowing waters around the world, as long as they are nutrient-rich enough for the delicate underwater plant. Humus muddy soils offer the chickweed the best conditions, so that it can survive in water depths of up to 10 meters. As a rule, however, the plants prefer areas between 0.5 and 1 m in lakes, ponds and backwaters, especially in areas protected from the wind. They usually swim freely in the water or are caught on other plants. The rough horn leaf does not form any actual roots with which it can cling to the ground. The feathery underwater plant absorbs the nutrients through root-like structures that form from transformed sprouts.

  • Water depth: mostly 0.5 to 1 meter
  • Light requirement: low to medium
  • muddy, humus-rich subsoil
  • nutrient-rich water
  • sheltered location
  • very adaptable to water hardness (5 to 18 degrees water hardness)
  • pH values ​​between 6.0 and 8.0


The Rough Hornblatt lives entirely under water. The plant either floats freely or is anchored to the ground or other aquatic plants without roots. However, the plants anchored in the ground form special root-like branches (so-called rhizoids) in order to be able to hold themselves better in the muddy underground. The mostly green, often reddish-looking stems can grow up to 100 centimeters long. Its fine, fragile leaves are arranged at short intervals in an almost ring-shaped manner around the stem and are once or twice forked. The chickweed is a relatively undemanding plant that only grows at one end (the shoot tip) and slowly dies at the other end.

To use

Hornleaf is not just any plant cultivated for its good looks. The underwater plant is a real all-rounder that is a real enrichment for many bodies of water:

1. Influence on the nutrient content
Plants living below the surface of the water – above all the chickweed – play a crucial role in maintaining the water quality in shallow, nutrient-rich bodies of water. Rough horn leaf has no roots, so it is forced to get its nutritional needs directly from the water in the area. By building up its own biomass during growth, it reduces the nutrient content of the water body. In addition, the horn leaf is able to filter out pollutants and store them in its biomass. It has another positive effect on water quality.

2. Oxygen supplier
Like all plants, the rough horn leaf also produces oxygen, which, as an aquatic plant, it releases into the water and not into the air. Oxygen is not only vital for all animals in the pond or aquarium, but also for the many bacteria in the water that break down organic waste and sludge. The aquatic plant is therefore very important for all underwater creatures, especially in summer, as there is often a lack of oxygen in the water at this time. In many cases, a lack of oxygen leads to fish deaths.

3. Algae Reduction
By fighting for nutrients and light, hornbill competes with other aquatic plants and algae. In addition, the aquatic plant produces its own chemical compounds that can reduce the growth of other plants. This can have a positive effect on a possible algal bloom, which otherwise occurs in water bodies on an annual basis. Therefore, waters where the Hornblatt is found are usually relatively clear. However, these plant-specific substances do not work on all algae.

Tip: The thread algae is largely insensitive to these active ingredients and not only spreads further, but also inhibits the vitality of the hornwort as an epiphytic plant. In the worst case, the finely branched leaves of the horn leaf clump together and die off.

4. Creation of habitats
The horn leaf has other advantages. It contributes to the structural diversity of a garden pond or aquarium and thus creates a variety of habitats. The more habitats are created, the greater the diversity of species that keeps the complex biotope intact as a small ecosystem.

  • Food basis: A fine biofilm forms on the leaves, which serves as food for many microorganisms
  • Safety: Dense populations protect small creatures from predators (hiding places for spawn, small fish or even midge larvae)
Note: If fish do not reproduce, this may be due to a lack of spawning grounds. The hornwort offers ideal conditions for this.

5. Softening of the water
In very hard (calcareous) water, which also has a high pH value (alkaline), a fine, white deposit of limescale forms on the leaves of the horn leaf. This is formed when the plant assimilates carbon from the calcareous water. In this way, the plant makes an important contribution to the decalcification of water (biogenic decalcification).


Each rough horn leaf forms both male and female flowers, which, however, grow very inconspicuously on the stem. This results in fertilization, which incidentally takes place via the water, very small seeds that ensure the spread of the hornwort. Much more frequently, however, the aquatic plant propagates via pieces of shoots, because the thin shoots break off very easily and then quickly develop into a new plant. In autumn, starchy winter buds form, which sink to the bottom of the pond. These buds will sprout again next spring as temperatures rise. All remaining plant parts die off in cold weather and sub-zero temperatures.

Problems in the cultivation of the horn leaf

The following also applies when keeping the rough horn blade: less is more! Even for the inexperienced garden pond or aquarium owner, it is easy to see that without human intervention, the water quality quickly loses again if the plant is simply given free rein to grow. Therefore, every gardener who uses the horn leaf in the pond in a targeted manner should observe the growth of the aquatic plant very closely.

  • first of all, a luxuriant growth can be seen
  • Once a week, pull out a few plants with the rake to check
  • if they are still fresh and juicy, everything is fine
  • if the horn starts to decompose, intervention is required
  • now the nutrient content is no longer sufficient for all plants
  • some specimens should be taken out of the pond
  • only leave enough plants in the water for them to grow well

In the beginning, it’s a bit difficult to find the perfect balance. For this reason, it should be checked weekly at first. If dying plants are found, at least a third of the plants are removed. If, after a week, there is still severe decomposition on the horn leaves that have been taken out, then more plants have to leave the pond, but less than the first time. The process is repeated until the plants that are brought out for inspection look fresh and vigorous again. The plant population in the pond should now be kept at this level.

Where is the horn blade out of place?

In two cases, the use of the horn reed is useless or completely counterproductive. Therefore, the water quality should be checked well in advance before the rough horn blade is used. The aquatic plant is unsuitable as an ornamental plant, as there is always a great deal of control associated with its cultivation.

  1. In all ponds where the water quality is already very good. Here the chickweed would not find good living conditions, would die and rot on the ground.
  2. In ponds with large amounts of thread algae. The filamentous algae get caught in the leaf whorls of the horn leaf, causing them to clump together and suffocate. In waters with thread algae, these must first be fished out before the rough horn blade is used.

cultivation in the aquarium

Consistently high temperatures and plenty of light offer the chickweed optimal living conditions in an aquarium. If there are fish in the tank, a CO2 supply is actually not necessary, but it supports growth. Ceratophyllum is known to absorb nutrients quickly. This makes the plant an ideal “weapon” in the fight against algae, especially since the rough horn leaf also produces a natural anti-algae agent.

Because of its rapid growth, the plant often has to be trimmed. While most parts of the plant die off in the garden pond in winter, the rough horn leaf grows in the aquarium all year round. For rejuvenation, the lower, older part is simply separated and the upper piece anchored back into the ground.

Ceratophyllum demersum should primarily be used in the background of the aquarium, where it forms nice, dense areas when used as a group. In the aquarium, the chickweed usually does not grow any attachment roots (rhizoids) in the gravelly soil, which is why the plants have to be pressed into the ground again and again.

Note: Pay attention to the weight rings on the plant when you buy it and leave them on the horn leaf when you put them in the aquarium.

Hibernation in the garden pond

Ceratophyllum demersum is incredibly well adapted to life under water. Native species of hornwort are hardy and are therefore the ideal aquatic plant for the garden pond. The gardener does not even have to do anything for the right winter storage, because in autumn the plant forms short sprouts that sink to the bottom. If the garden pond is deep enough and the bottom areas are therefore free of ice, the sprouts hibernate there and sprout again in spring when temperatures rise.

Tip: If you cultivate hornwort in a bucket on the balcony, you can bring the plants indoors over the winter and overwinter them in an old aquarium or a smaller bucket with some pond water. Set up in partial shade.

With a little attention, control and a good feel, the rough horn leaf becomes a valuable helper for good water quality in the garden pond or aquarium. However, if you use the plant to decimate algae or to remove excess nutrients, you must not leave the plant to its own devices, as this usually leads to the exact opposite after initial success.

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