How to Grow Duckweed in an Aquarium

Ducks love to eat duckweed.

Ponds defined as “dirty” or “scummy” usually have a lot of duckweed in them. This plant, made of little leaf-looking petals that stick together, can cover a pond with a layer up to an inch thick. It provides shade to some fish and a source of nutrients to others. Grow it in your aquarium with the incorrect fish and you may find it eaten before you can grow it to a sustainable volume.

Things You'll Need

• Lunker fish

Instructions

1. Fill a 20-gallon or larger aquarium up to three inches from the top. You can use a smaller aquarium, but the duckweed may grow too quickly to keep under control.

2. Introduce one or more types of lunker fish, such as an oscar, to the aquarium. These fish like to live under duckweed and produce chemicals the plant live off of, such as carbon dioxide and ammonia.

3. Set the aquarium in a location where it gets lots of sunlight. If it can't get sunlight throughout the entire day, ensure it gets sunlight at least half of the time.

4. Buy duckweed from your local pet store. An associate can help you package and transport it.

5. Put the duckweed in the aquarium water. It will stay on the surface. Allow it to grow until it covers two-thirds of the tank and is thin enough that you can still see the fish swimming beneath it. Use a net to remove some of the duckweed if it grows too thick. Monitor daily. Duckweed grows quickly.

Tips & Warnings

• Do not put koi, goldfish or carp into the tank. They will eat all of the duckweed. If you move the duckweed to a pond, keep the ducks away. They will also eat all of the plant.

References

• Aqualand Fact Sheets: Duckweed – Lemna minor
• “Daily Puppy”; How to Get Duckweed; Craig Sernotti