Identification of duckweed in your aquarium

You first want to make sure that you have actual duckweed in your aquarium. There are lots of floating plants and some look like duckweed but are not as much of a pain to deal with.

Observe the plant's appearance: Take a close look at the plant's features. Duckweed consists of small, floating fronds that are typically oval or round in shape leaf type clover. The number of leaves, or fronds, on a single duckweed plant can vary depending on the species and environmental conditions. They have a smooth texture and a vibrant green color when young but gain texture on top of it when it gets bigger. To me it looks almost like how a cat’s tongue would look like with little hairs.

Look for roots: Pay attention to the presence of root hairs. Each frond of duckweed usually has many root hairs hanging below it. These delicate structures aid in buoyancy and provide stability. These roots can reach up to 2 inches in length.

Note the growth pattern: Duckweed tends to form dense mats on the water's surface. These mats can spread rapidly and cover a significant area, creating a green carpet-like appearance. In some cases, it can even grow under other duckweed making the matt double maybe even triple layered deep.

Consider the habitat: Duckweed is commonly found in freshwater environments, such as ponds, lakes, and slow-moving streams. It thrives in calm or still waters where it can float and receive adequate sunlight for photosynthesis.

Compare with reference images: To confirm your identification, compare the plant you have observed with reliable reference images of duckweed. Feel free to use the images in this article.

Ok so the panic is on you have confirmed it. The duckweed invasion has struck! Brace yourself for the tiny green conquerors taking over your aquatic kingdom. It's like a rebellious plant rebellion, plotting to turn your serene aquarium into a chaotic jungle! Prepare for the battle of a lifetime as you face off against these miniature green monsters. Will you emerge victorious or be swallowed by a sea of floating fronds? It's time to summon your inner plant warrior and don your armor of determination. Remember, laughter is the best weapon against adversity. So, don't forget to chuckle at the absurdity of this miniature aquatic takeover. Embrace the quirkiness of the situation and let humor be your shield in the face of duckweed chaos. Together, with a dash of humor and a sprinkle of determination, you shall triumph over the duckweed invaders. Reclaim your aquarium's serenity and restore order to your aquatic realm. May your journey be filled with laughter and may the duckweed retreat in the face of your mighty aquatic humor!

So, is duckweed in my aquarium bad?

The short answer is no. Duckweed actually has many benefits and a few disadvantages, but to many seasoned aquarists the disadvantages can develop into a pet peeve due to it’s excessive growth and ability to outcompete other plants. 

Aggressive growth: Duckweed has a remarkable ability to reproduce quickly, forming dense colonies that cover the water's surface. This rapid growth can outcompete other aquatic plants, obstructing their access to light and nutrients.

Light blockage: The dense mats of duckweed can block sunlight from reaching the submerged plants in the aquarium or pond. This can hinder their growth and photosynthesis, leading to an imbalance in the aquatic ecosystem. Light for thee and not for me.

Nutrient absorption: Duckweed absorbs nutrients, such as nitrogen and phosphorus, from the water column. While this can help in natural water purification, it can cause your plants in the aquarium to not get enough nutrients. If you notice your plants turning yellow or losing color, you might be a victim!

Fragmentation and regrowth: Even if you attempt to remove duckweed manually, it can regenerate from small fragments left behind. This ability to regrow from tiny pieces makes complete eradication a challenging task. The odds you will get it all are almost impossible. It can stick anywhere in your aquarium; I have even seen it wedged in gravel at times!

Impact on fish: In some cases, duckweed can create issues for fish and other aquatic animals. It can reduce oxygen exchange at the water's surface, potentially leading to oxygen depletion in poorly oxygenated water bodies. Believe it or not these plants don’t produce a lot of oxygen for your aquarium because half the plant is normally out of the water.

Hitchhiking pests: Duckweed can sometimes carry or provide a habitat for unwanted pests, such as mosquito larvae or snails. This may introduce additional challenges or pests into your aquarium or pond.

Maintenance challenges: Managing duckweed growth can be challenging. Manual removal can be time-consuming, especially since duckweed fragments easily and can regrow from small remnants. Controlling its spread may require continuous efforts and careful monitoring.

Well why do some people say duckweed isn’t that bad, dare they say it is even good for your aquarium.

There are several positive effects to having duckweed in your aquarium as listed below.

Water purification: Duckweed is efficient at absorbing excess nutrients, such as nitrogen and phosphorus, from the water. This can help in reducing nutrient pollution and improving water quality in lakes, ponds, and wastewater treatment systems. It acts as a natural filter, removing pollutants and promoting healthier aquatic ecosystems.

Fish food: Duckweed has a high protein content, making it a potential source of fish feed. It can be utilized as a supplementary or alternative feed for livestock, poultry, and fish. Its rapid growth and nutrient-rich composition make it a sustainable and cost-effective feed option. We will do in depth about what fish will eat the stuff!

Phytoremediation: Due to its ability to accumulate heavy metals and other contaminants, duckweed has been employed in phytoremediation projects. It can help in the cleanup of contaminated water bodies, absorbing pollutants and aiding in environmental remediation efforts. The most common metal you would want to reduce is copper, which could be deadly to most inverts and fish.  These plants will absorb trace amounts of copper out of the water and if you are manually throwing these plants out you are removing trace amounts of copper and other unwanted metals. 

Wildlife habitat: Duckweed provides a habitat and food source for various organisms. It offers shelter for insects, small fish, amphibians, and waterfowl. Its presence in aquatic ecosystems supports biodiversity and contributes to the overall health of the ecosystem. I see small fish always searching duck weed roots for small prey and even more commonly I see shrimp love to pick on duckweed roots. Sometimes you will catch a shrimp who weighs too much for the duckweed and it will fall into the aquarium, then you can watch the shrimp abandon ship and have the duckweed float back up.

Natural aesthetic: Duckweed can add a natural and visually appealing touch to your aquarium. The vibrant green color and floating mats create a serene and natural ambiance, replicating the look and feel of a peaceful pond or lake.

Shade and shelter: The dense mats of duckweed provide shade and shelter for your aquarium inhabitants. Fish and other aquatic organisms can find refuge and feel more secure, especially for shy or delicate species that prefer a more secluded environment. Fish like betta don’t like direct light and would love to have some duckweed in the aquarium to reduce direct light.

Fry protection: Duckweed offers a hiding place for fish fry and other small aquatic organisms. The coverage provided by the mats can protect the young and vulnerable inhabitants from predation, increasing their chances of survival. The roots will go down further than you think offering a good inch or two of protection from the surface.

Low maintenance: Duckweed is relatively low maintenance and requires minimal care. It can grow well in a variety of lighting conditions and can thrive in both tropical and temperate aquarium setups. Its ability to absorb excess nutrients can help reduce the frequency of water changes and simplify overall aquarium maintenance.

Now you are probably thinking to yourself maybe it isn’t so bad that I have duckweed in my aquarium and honestly in my opinion I totally agree. This isn’t the end of the world and as long as your are willing to take a hand or two of it and throw it out each week it wont be too bad. But if that is too much for you might want to consider a secondary option like use of livestock. Some fish will eat duckweed! I mean don’t expect to have any other plants in the tank because they will probably eat that too but shoot it might be worth it to get rid of that duckweed!

Can I remove duckweed from my aquarium?

You can, but it is extremely difficult. The only guaranteed way would be to fully empty your aquarium and let the system dry out. These plants are very resilient and will survive days out of the water, so you should leave the aquarium fully dry for several weeks. After that you can attempt to re-establish the aquarium.

Common mistakes when trying to remove duckweed permanently.

• Failing to manually remove as much duckweed as possible before attempts to eradicate it with other methods.
• Failing to clean the filter or sump for stray pieces of duckweed.
• Failing to vacuum the substrate where pieces of duckweed could be wedged under.
• Attempting to use chemicals will normally not work and will likely harm everything else in your aquarium.
• Trying to starve the plant of light for a few days. These plants can go without light longer than almost any other plant in the hobby.
• Not removing any hardscape that could be hiding stray duckweed pieces.

Since it is so difficult to fully remove duckweed, many aquarists choose the option to just manage the population of duckweed in their aquarium. Some of the methods below are used to control the duckweed population in your tank.

Manual Removal: Using a fine-mesh net or your hand, gently skim the water surface to scoop up the duckweed. Be thorough and remove as much duckweed as possible. Repeat this process regularly to prevent its regrowth.

Surface Skimmer: Installing a surface skimmer can help collect and remove duckweed from the water's surface. The skimmer creates a flow that pulls the duckweed towards it, allowing for easier removal.

Water Changes: Performing regular water changes can help dilute the nutrients in the water, which can contribute to duckweed growth. Replace a portion of the water with fresh, clean water to help control the duckweed population. Now keep in mind that this is only useful if you have no other plants because this is attempting to starve the duckweed in your aquarium out, but if you have other plants, you will also starve them out.

Aeration and Water Circulation: Increasing water movement and aeration can discourage duckweed growth. Use an air pump, water pump, or fountain to create water circulation, which can help disrupt the duckweed mats and prevent them from spreading. Now I am talking about a lot of surface movement not just a little bit of movement or a few bubbles hitting the surface.

Some people will use livestock to better control the population of duckweed. Example fish that eat duckweed are as listed.

Goldfish (Carassius auratus): Goldfish are omnivorous and will consume a variety of plant matter, including duckweed. They have a voracious appetite and can readily graze on the floating mats of duckweed in an aquarium or pond. Introducing goldfish to your aquarium can help control the growth of duckweed, as they will actively consume it as part of their diet. However, it's important to note that the effectiveness of goldfish in managing duckweed can vary depending on factors such as the size of the population and the density of duckweed in the tank.

Convict Cichlid (Amatitlania nigrofasciata): Convict cichlids are omnivorous and will eat a variety of food, including plant matter. While they may not specifically target duckweed, they have been reported to consume it if present in the aquarium.

Jack Dempsey Cichlid (Rocio octofasciata): Jack Dempsey cichlids are another omnivorous species that may eat duckweed if offered. However, their primary diet consists of meaty foods, and their consumption of duckweed may vary.

Koi (Cyprinus carpio) is known to eat duckweed. Koi is omnivorous and will consume a wide range of food, including various types of plant matter. Duckweed is often included in the diet of koi kept in ponds or larger water bodies.

Grass Carp (Ctenopharyngodon idella) are known to eat duckweed. They are herbivorous fish that have a strong appetite for aquatic vegetation, including duckweed. Grass carp can be effective in controlling the growth of duckweed in larger ponds or water bodies.

Tilapia (Oreochromis niloticus) fish are herbivorous and have a natural appetite for various types of aquatic vegetation, including duckweed. They can be effective in controlling the growth of duckweed in aquariums, ponds, or aquaponic systems.

So, I get it none of these fish will fit into your ten-gallon aquarium. Most of these fish are best for either really big fish tanks or maybe even ponds. It just shows you that it takes a monster to defeat a monster. For everyone who has a small tank you are going to have to stick with the options that don’t involve livestock.

Final thoughts

So, all of this isn’t appealing to me, what do I do? Prevention is the best method. Do your best to make sure duckweed never has a chance to enter your aquarium. This would mean you need to quarantine any plants or wet hardscape. You might find a piece of duckweed stuck to the side of driftwood, hardscape or wedged between new plants. If you already have it in your tank full removal is very difficult. Duckweed has existed for Millions of years and has adapted to almost anything that was thrown at it, so it’s safe to say this won’t be easy to beat it in your aquarium. In my opinion the best way to handle duckweed once you have it is to just throw out some of it every week just like you do with water changes. It will just become one extra task on your schedule. So don’t fret this isn’t the end of the world, it is just the start of a new chapter!