Ceratophyllum demersum, also known as Hornwort, is a very popular aquatic plant in the aquarium trade due to its rapid growth and many beneficial properties for the aquarium. Here are some maintenance tips:

1. Lighting: Ceratophyllum demersum is a plant that can thrive in low to medium lighting conditions.

2. Temperature: between 15 and 28 degrees Celsius, but can tolerate higher temperatures.

3. Nutrients: Ceratophyllum demersum is a plant that can take up nutrients directly from water, but it will also benefit from a nutrient-rich substrate and a supply of liquid aquatic plant fertilizers.

4. CO2: The plant can thrive without an additional supply of CO2, but extra CO2 will help boost growth and density.

5. Maintenance: The Ceratophyllum demersum does not need to be planted in the substrate, but can simply be floating. It is important to regularly remove dead or damaged parts of the plant to prevent them from rotting and polluting the aquarium water. Regular pruning of the plant will also promote denser growth.

6. Placement: Ceratophyllum demersum can be placed anywhere in the aquarium, but it will be more effective in controlling algae if placed on the surface.