How to Care for Ceratophyllum demersum (Hornwort)

Korean name: 붕어마름

An aquatic plant that grows underwater, providing oxygen and purifying water in aquariums. It grows well with fish and grows quickly.

Key facts

Care Guide

Detailed care guide

Hornwort is a submerged plant that grows well in aquariums, helping to oxygenate the water and keep it clean. It's easy to care for, making it a great aquatic plant for beginners.

Watering

Hornwort only stays healthy in a fully submerged environment. If it dries out above the water's surface, the leaf tips can brown or the plant can dry out.

Light

This plant likes medium to bright light. If light is lacking, the stem can stretch and become leggy and the leaves can grow sparse, so keep it somewhere with good light.

Humidity

Since it always grows underwater, there's no need to manage surrounding humidity separately. It's rarely short on moisture, but keep an eye on the water level so it doesn't drop from evaporation.

Temperature

It grows well between 10–28°C. Growth can suffer if the temperature is too low or too high, so keep it within this range.

A common first-timer mistake

People often get confused since it's grown without soil, mistakenly potting it or taking it out of the water. It must be kept fully submerged at all times to grow healthy.

If you have pets

Hornwort is not known to be toxic to pets. That said, eating too much of any plant can cause an upset stomach, so if your pet chews on it habitually, move it out of reach.

Care by Season

Hornwort grows well year-round at 10–28°C. No special seasonal care is needed in an indoor tank, and as long as the indoor temperature doesn't swing drastically by season, growth won't be seriously affected. In hot weather, water evaporates faster, so check the water level often and top it off. When it's cold, be careful not to let the water temperature drop suddenly.

Common Problems and Fixes

A lack of light can cause the stem to grow weak and leggy, and the leaves can thin out in dark spots. Overly bright light can stress the plant, but if the water is too cloudy, less light gets through, which also hurts growth. If it's left dry or lacking water, the leaf tips can dry out and brown, and if the water is too murky or lacks circulation, the leaves can turn yellow, so manage the water carefully.

Repotting and Propagation

Hornwort has no roots and doesn't need soil, so repotting isn't necessary. To propagate, cut off a piece of the stem and move it to another tank, and it will naturally grow into a new plant. It grows fast, so if it gets too dense, trim some back to keep balance. Propagation is very easy, so even beginners can try it.

Who It's Good For

It's a great fit for anyone who wants to grow a plant alongside fish in an aquarium or tank, or who wants both oxygenation and water quality management. It's not difficult to care for and can thrive without special equipment, making it ideal for beginners starting out with aquatic plants. Since it propagates naturally, it's also great if you want to change up a plain tank. It's a good fit for anyone who wants to enjoy a touch of underwater greenery without complicated care, even in a busy daily life.

Written by AI from the care facts in this entry. Treat it as a starting point.

Common questions

How often should you water Ceratophyllum demersum?

Grows in fully submerged conditions.

Where should you keep Ceratophyllum demersum?

It likes Medium to bright light. You can grow it indoors. Use No soil needed (no roots).

Is Ceratophyllum demersum safe around pets?

No known toxicity, so it is fine to keep around pets.

Is Ceratophyllum demersum good for beginners?

Difficulty: Easy. It is forgiving enough for a first plant. Keep it around 10~28°C. Humidity: Aquatic environment. Fertilise Aquatic plant fertilizer.