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4 Methods to Get Rid of Duckweed in Your Pond

4 Methods to Get Rid of Duckweed in Your Pond

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At first glance, it might’ve seemed harmless, but after a few days, you may be noticing your pond’s surface turn green with duckweed.

The pond plant has a significantly fast growth rate. It can double its quantity by 16 hours to two days. This expansion depends on the duckweed’s conditions.

When provided with optimal hot temperatures and a nutrient-dense landscape, it’ll quantify like no tomorrow.

Stick around to learn more about duckweed, where it comes from, its effects, and how you can get rid of it.

Identifying Duckweed

Duckweed, often confused with algae, is a round-shaped pond plant. The plant is usually found in stagnant waters and may cover a pond’s entire surface due to its invasive nature.

They survive on nitrogen and phosphate minerals. The plant can multiply in as little as a day. One parent can breed a hair-raising 17,500 plants when left for two weeks.

You can locate the species in aerated ponds if the waters are nutrient-dense. Besides that, you can grow duckweed in your garden as long as you enforce population control methods.

They can benefit your pond by absorbing excess nutrients. Duckweed, or water lens, is also a suitable snack for your koi or other pond fish to munch on.

Oxygen levels can decrease if the pond plant’s population goes overboard. Consequently, the reduced aeration can harm your fish and underwater plant life.


Duckweeds are aquatic perennials that barely exceed a quarter inch in diameter. They have thin strands of root flowing underneath each shiny, round leaf.

The pond plant species, when spread, resemble a green carpet layer on your pond’s surface.

Causes of Duckweed Infestation

Duckweed infestation usually comes from outside sources. For instance, you may have purchased a new pond plant that, unbeknownst to you, is harvesting duckweed seeds.

Consequently, quarantining the plant is essential before incorporating it into your landscape feature.

Some factors can be out of your control, like erosion, wildlife deposits, and environmental conditions.

Wildlife Contamination

Birds and waterfowl can carry duckweed specimens to your pond. The wildlife brings the plant in the form of barely-visible seeds that float.

Once the conditions are right, the pit can result in a booming population.


Your pond may connect to agricultural land or lawn areas teeming with fertilizer. Erosion can transfer the minerals into your pond and deposit duckweed.

Subsequently, you can control the runoff by decreasing fertilizer use around your pond.

Ideal Environment

Duckweed thrives in nutrient-dense brackish and clear ponds. Temperatures ranging between 42 to 91 degrees F can cultivate the invasive species.

Water lenses prefer tropical and high-temperature environments. When exposed to too much wind, they don’t grow roots.

The floating plants evolved to survive through harsh winters. Duckweeds develop turions or specialized shoots that allow them to sink underwater for hibernation.

Thanks to natural selection, these plants can inherently extend their roots as nutrient levels in the water deplete. They lengthen their shoots to cover more surface area and find minerals.

Methods to Get Rid of Duckweed in a Pond

While there are multiple methods to remove duckweed, implementing one alone won’t be as effective. For this reason, we suggest following two to three of the methods mentioned.

1 – Physical Method

One of the first methods that likely popped into your head is removing the duckweed physically.

The physical way is well-suited to ponds with fish since it’s the least harmful and doesn’t use chemicals.

You can use nets, skimmers, rakes, or a pond vacuum to remove the duckweed infestation. Luckily, duckweed is visible, unlike algae.

Once you’ve sucked and skimmed all the pond plant’s remains, dispose of them. Make sure they don’t runoff back into your pond via wildlife.

The physical method doesn’t work alone. Subsequently, you’ll want to implement other ways to eliminate the duckweed.

2 – Wildlife Control

The good news is that you can enlist mother nature’s food chain to control duckweed populations. In other words, you can add natural predators.

These duckweed eaters can include koi, goldfish, tilapia, and domesticated waterfowl. In the latter’s case, you’ll want to find a way to keep wild waterfowl animals out of your pond.

It’ll limit the risk of duckweed transfer. To do so, keep a surface net on the pond to discourage them from entering the premises.

Alternatively, you can raise the bank’s levels or decrease the number of vegetation surrounding the pond.

When adding duckweed prey, reduce their feed intake. That way, they’ll gravitate to the round pond plants.

3 – Chemical Method

Luckily, the market has no shortage of duckweed-killing herbicides. Nevertheless, the chemical route isn’t the best for your fish and plant’s health.

Overuse of the chemical can damage your pond’s ecosystem and balance. Aside from that, when purchasing the herbicide, look out for active ingredients such as,


The chemical acts as a photosynthesis inhibitor on duckweed. In turn, it’ll hinder the plant’s ability to use sunlight for energy.

Subsequently, the population will weaken and decay. Besides that, the herbicide ingredient can take around 30 days to offer effective results.

Nonetheless, it can manage your duckweed infestation for about 90 days. The reason behind this is that the chemical remains stagnant for prolonged periods.

For this reason, if there’s too much water flow, the herbicide will be less successful. Make sure to consult the directions of the product for the correct quantity.

4 – Aeration Method

Duckweed often lives in quiet waters with minimal wind movements. For this reason, aerating your pond can help hinder its ideal environment.

A bubble aeration system will inhibit duckweed growth and provide a cleaner pond. Plus, the air circulation will promote oxygen levels, which may have depleted from the infestation.

Subsequently, it’ll benefit your fish and submerged pond plants. Additionally, the air will release harmful gases embedded in the pond’s bottom layer caused by waste accumulation.

Duckweed Prevention

Maintaining a duckweed-free pond involves altering its ideal environment. For instance, the invasive plant is known to float in slow-moving waters.

In turn, adding a water pump can hurt its chances of survival. Here are other long-term prevention methods to consider.

Maintaining Pond Hygiene

When waste is left to collect on the pond floor, it releases nutrients for duckweed consumption. In turn, you need to remove the invasive plant’s source of sustenance through regular upkeep.

To do so, we recommend installing a surface net to keep any debris or leaves from falling and decaying. Maintaining your fish’s diet by avoiding overfeeding is also essential.

You’ll also want to clean your filtration system weekly with a garden hose. Overall, a clean pond will be less likely to house an overabundance of duckweed.

Bio Dredge the Pond

Luckily, you can pop in a few pellets of beneficial bacteria in your pond to dredge or remove excess waste and nutrients.

It’ll catalyze the process of breaking down the decaying organic matter. Keep your pond well-aerated while using this method.

The prevention method is less costly and doesn’t require a permit. Plus, you won’t need any equipment.

Effects of Duckweed in a Pond

Duckweed can pose negative and positive impacts on a pond.

Positive Effects

Positive-wise, the plant offers water purification, algae control, and hiding spots for prey. Additionally, water lenses reduce water evaporation rates and save costs on fish feed.

Negative Effects

As your duckweed population booms, so does its demand for nutrients. Consequently, the plant can compete for minerals with other surrounding pond plants.

In addition, the plant acts as a blanket, hoarding all the sunlight from reaching underwater foliage. The latter will likely lose energy and its ability to photosynthesize.

Does Pond Dye Kill Duckweed?

Whether or not pond dye can kill duckweed is still speculative. On one hand, the dye can darken the waters and limit the pond plant’s sunlight absorption.

On the other hand, pond dye isn’t a fool-proof method to eliminate the plant’s infestation.

For this reason, it’s best to resort to other more effective prevention measures, such as pond hygiene maintenance and installing an aeration system.

Final Thoughts

Duckweeds, also known as the smallest-sized flowering plant, enjoy floating in waters filled with nitrogen and phosphate.

The plant can creep into your pond via waterfowls. Since the latter enjoys snacking on the plant, it may likely carry some seeds in its feathers that can transfer to your area.

Getting rid of the plant involves applying several methods. Firstly, you’ll want to manually remove the population with a skimmer, shovel, or vacuum.

Next, you can add a filtration and aeration system to discourage the duckweed’s growth. Lastly, add active herbicides to remove any remaining leaves lingering on the surface.


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