Do Goldfish Eat Duckweed? How much do They Eat

Have you been thinking of including duckweed in your Goldfish’s diet? Do goldfish eat duckweed?

Is it any good for them? Should it be part of their diet and how much they can eat it.

I will cover all this and more below.

Do Goldfish Eat Duckweed

Yes! Goldfish eat duckweed, and it is not harmful to them. It offers a great snack for your fish because it is tasty and nutritious. So, Goldfish find the plant delicious and will eat it to their satisfaction.

Goldfish are omnivorous and enjoy a varied diet that includes both plant matter and small organisms. Duckweed can be a nutritious addition to their diet as it contains protein, carbohydrates, and other nutrients.

It is important to ensure that the duckweed is sourced from a clean and pesticide-free environment to avoid any potential contaminants. Introduce duckweed gradually to your goldfish and observe their response to ensure they tolerate it well.

How Much Duckweed Can Goldfish Eat?

Goldfish finds duckweed tasty and edible. This fish species is grazing fish that will eat their fair share of the tank’s duckweed plant. Hungry Goldfish will eat the plant until they feel satisfied.

You can view duckweed as the grass of the tank. It can increase and cover the entire tank’s surface, but your Goldfish will not let this happen. The fish will eat the plant as long as they need something to munch.

It might not be possible to estimate the exact amount of duckweed a Goldfish can eat. But the known fact is that they will eat the plant as long as they are hungry. They won’t stop until they are satisfied.

The only way to stop them from eating the plant is to provide them alternative food. They might look away from the plant when they are not hungry. But Goldfish will go back as soon as they feel like having some snacks.

Will Goldfish Eat All The Duckweed

Yes, However, whether they will eat all the duckweed entirely depends on various factors, including the quantity of duckweed available, the size and number of goldfish, and the availability of other food sources.

If the tank or pond has a substantial amount of duckweed, it is possible that goldfish may not eat it all, especially if there are other food options available. However, if duckweed is the primary or only food source provided, goldfish may consume it until it is depleted.

What Are The Advantages & Disadvantages Of Eating Duckweed?


Eating duckweed for Goldfish is not just to prevent them from being hungry. It is tasty and also offers a high nutritional value. It supplies Goldfish with vitamins, proteins, and other essential trace elements.

Here are some of the benefits of eating duckweed, particularly for duckweed.

  • It is Rich in Protein : Protein is one of the essential nutrients necessary for fish growth and survival. Goldfish is not an exception to this case. They need a rich protein supply for their development, and duckweed helps them with this. Full-grown duckweed can contain up to 40% protein. This percentage is sufficient to supply Goldfish with enough protein necessary for their growth and survival. Besides, the protein in duckweed is easily absorbable into the fish’s body.
  • Efficient Source of Vitamin : Vitamins are an essential part of fish’s diet. It is necessary for their body’s functioning and improves the body’s resistance to diseases and infections. It also aids Goldfish’s digestion and mitigates the possibility of constipation. Duckweed is particularly rich in Vitamin A and B. These vitamins are necessary for steroid hormone and folic acid synthesis in fish. It also prevents conditions like abnormal swimming, lethargy, and organ malfunction.
  • Duckweed Supplies Essential Trace Elements : Trace elements are useful in small amounts and essential for the growth of the fish. Duckweed is a rich source of potassium and calcium, which are critical for Goldfish. It also includes other pigments, especially xanthophyll and carotene that helps with fish growth.
  • Offers Other Dietary Supplements : Duckweed will help your fish to get nutritional supplements they might not get from other food sources. It can fill the void for the veggie needs of fish while also providing some environmental benefits.


Duckweed is a floating plant that is common in Goldfish tanks. The plant is not harmful to Goldfish, and that is why you can feed it to them.

Besides the fact that it is tasty, it also provides numerous nutrients for the fish. Goldfish feed it on the plant as snacks because they find it delicious.

It can form a good part of their fish tank. Some aquarists add Goldfish to ponds as a means to control duckweed. The fish will happily munch on the plant once they find it in their tank, and it won’t cause any harm.

The only way duckweed can be harmful is when they grow excessively in the tank. In this case, they will deplete oxygen levels which are dangerous for the fish.

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How to Grow Duckweed for Goldfish

Growing duckweed for goldfish is relatively simple. Here are the steps to follow:

  • Set up a suitable container: Use a shallow container, such as a plastic tub or aquarium, that can hold water and provide enough surface area for the duckweed to grow. Ensure the container is clean and free from any potential contaminants.
  • Fill the container with water: Use dechlorinated water, either from a water conditioner or by letting tap water sit for 24 hours to allow chlorine to dissipate.
  • Introduce duckweed: Obtain a small amount of duckweed from a reliable source, such as an aquarium store or another pond. Gently spread the duckweed across the water’s surface. Duckweed will multiply rapidly under favorable conditions.
  • Provide adequate light: Duckweed requires ample light to grow. Place the container in a well-lit area, either indoors near a window or outdoors where it can receive direct or indirect sunlight.
  • Maintain water quality: Regularly monitor and maintain water quality parameters such as temperature, pH, and ammonia levels. Perform water changes as needed to keep the water clean and healthy for both the duckweed and goldfish.
  • Harvest and feed the duckweed to goldfish: Once the duckweed has multiplied and formed a dense mat, you can start harvesting it for your goldfish. Use a net or scoop to remove portions of the duckweed from the container and offer it to your goldfish as part of their diet.

What Other Pond Fish Eat Duckweed

There are several other pond fish species that may eat duckweed as part of their diet. Some of these fish include:

  • Koi: Koi are popular pond fish that can consume duckweed. They have a hearty appetite and are known to eat a variety of aquatic plants, including duckweed.
  • Grass carp (White Amur): Grass carp are herbivorous fish that feed primarily on aquatic vegetation, including duckweed. They can be effective in controlling the growth of duckweed in ponds.
  • Tilapia: Tilapia are omnivorous fish that can consume duckweed. They are often used in aquaculture systems to control aquatic plants, including duckweed.
  • Common carp: Common carp have a varied diet and can eat duckweed along with other vegetation and small organisms.

Frequently Asked Questions

Will Goldfish Control Duckweed?

Goldfish can help control the growth of duckweed in a pond or tank, but they may not completely eradicate it. Goldfish are known to eat duckweed as part of their diet, and their grazing can help keep the population in check. However, several factors can influence the effectiveness of goldfish in controlling duckweed:

  • Population size: The number of goldfish relative to the amount of duckweed plays a role. If there are too few goldfish compared to the amount of duckweed, they may not be able to consume it all.
  • Appetite and preference: Goldfish have individual preferences and appetites, so some may eat more duckweed than others. Some goldfish may prefer other food sources over duckweed, reducing their impact on its growth.
  • Tank or pond conditions: The size of the tank or pond, water quality, and availability of other food sources can affect how much duckweed goldfish consume. If there are ample alternative food sources, goldfish may not focus solely on eating duckweed.

Does Duckweed Oxygenate Water?

Like every other living thing, fish need oxygen to survive. Live plants usually add more oxygen to the tank as they photosynthesize. Duckweed adds little oxygen to the tank, but they are not as effective as some other plants.

Duckweed is a floating plant and can cover the tank’s entire surface. They are one of the smallest tank plants, and one can easily mistake them for algae. It is only beneficial if you let them grow moderately in the tank.

Excessive growth of duckweed in Goldfish tanks can cause more harm than good. Overgrowth of duckweed in the tank will negatively affect the oxygen level in the tank. It can reduce the oxygen level of the tank to a point where it can kill your fish.

However, Goldfish feeding is one of the natural ways to control the growth of your duckweed. You can also use another physical and chemical control method that won’t harm your fish.

Does Duckweed Clean Water?

Water cleanliness and water quality are crucial factors that influence the survival of a fish in the tank. One of the main reasons why people include live plants in their tank is to aid biological cleaning. Duckweed is not an exception because it can help you clean the water.

This floating plant uses a method called “water scrubbing” to clean the water. It can use this method to get rid of toxins and heavy metals in the tank.

Also, it uses some organic elements in the tank as part of its nutrients for growth. It also uses the carbon oxide waste in the fish tank as an essential part of photosynthesis.


Duckweed is a floating plant common in Goldfish tanks. The plant is small and can be mistaken for algae. Goldfish find this plant edible, and they will munch on it as often as they get hungry.

Goldfish can eat duckweed till they feel satisfied. The plant is tasty and serves as a rich source of essential nutrients like protein, vitamins, and other trace elements. However, it is vital to control the growth of duckweed in your fish tank.

The most common fish to keep in a pond is koi, but do koi and goldfish get on? Check out here for more information

John Brandon

John has kept fish all his life (since he was about 5). He started with keeping guppies and fell in love with fish keeping almost straight away. That was 40 odd years ago. These days John still keeps fish and currently has two large tanks where he keeps many different types of fish such as Angelfish, Neon Tetras, Goldfish, Guppies and many more.