Pond weeds can be a huge nuisance for any pond owner, but certain pond chemicals, known as herbicides, can be a very effective way to eliminate many species of common pond weeds. At Healthy Ponds, we sell several varieties of SePRO’s Sonar® herbicides, and these can be an effective and easy-to-apply solution for pond weed issues.


Before we talk about weed control, we do want to talk about our products for a minute. We sell a variety of pond treatment products, including chemicals and all-natural products. Please do not confuse our chemicals with our all-natural products. Healthy Ponds’ natural products are not classified as algaecides or herbicides. Now, let’s move on to the pond weed treatment process.


Step One – Identifying Your “Weeds”

There are many types of pond weeds, but before you treat the weeds with pond chemicals, you need to know which weeds are present in your pond. In some cases, you might not be dealing with a weed at all, but rather some type of algae, in which case you would need to use copper algaecide instead of an herbicide.

Additionally, there are several varieties of SePRO’s Sonar® herbicide, and each is formulated to eliminate specific pond weeds, so knowing what type of weeds you have is crucial before you select a product.

There are many weeds that we find in ponds throughout the United States. Some are floating, some are emersed and others are submersed. Here’s a quick list of the different species you might encounter in your pond depending on your location.


Emersed Plants:

  • Allligatorweed
  • American Frogbit
  • American Lotus
  • Arrowhead
  • Bacopa
  • Big Floatingheart
  • Bulrush
  • Cattail
  • Creeping Waterprimrose
  • Floating Water Hyacinth
  • Parrotfeather
  • Pickleweed
  • Smartweed
  • Spatterdock
  • Spikerush
  • Water Lily
  • Water Pennywort
  • Waterpurslane
  • Watershield


Floating Plants:

  • Common Duckweed
  • Common Watermeal
  • Salvinia
  • Waterlettuce


Submersed Plants:

  • Bladderwort
  • Common Coontail
  • Common elodea
  • Egeria
  • Fanwort
  • Hydrilla
  • Naiad
  • Pondweed
  • Tapegrass
  • Watermilfoil


Once you’ve identified the weeds in your pond, it’s time to select your pond chemicals. Sonar comes in several varieties, including Sonar® Q, Sonar® A.S. and Sonar® RTU. For instance, Sonar® RTU can be used to control bladderwort, common coontail, duckweed, Egeria, common elodea, fanwort, hydrilla, naiad, paragrass, spatterdock, water lily and most types of pondweed and watermilfoil.


If you aren’t sure which products to use, we can help. At Healthy Ponds, we offer free personalized water treatment plans for any size water feature at https://healthyponds.com/free-pond-plan/. You also can check out our product information pages for each type of Sonar® herbicide. These provide more detailed information about the types of pond weeds that are fully controlled or partially controlled by that specific product.


Sonar® Q



Sonar® A.S.



Sonar® RTU



Step Two – Applying Your Pond Chemicals

Each type of Sonar® has a different application process, but unlike with copper algaecides where you often apply directly to algae, you don’t have to come into contact with the weeds in order for the herbicide to work.


With Sonar® A.S., you spray the pond chemicals into the pond, preferably from the middle or from the banks of the pond. If you don’t have a sprayer, you can dilute the herbicide according to labeled rates and simply empty the herbicide into the pond. It takes about 15 to 30 days to see the effects of Sonar® A.S. At that point, the weeds should be turning white.


Sonar® Q comes in pellet form, and you can spread the pellets near the bank of your pond. With Sonar® Q, it typically takes about 2-4 weeks before plants start turning white, and sometimes even up to 10 weeks. While this might seem like a long time, this slow rate of control is beneficial because it decreases the likelihood of a severe drop in oxygen levels in your pond water, which can harm fish.


While Sonar® Q and Sonar® A.S. aren’t difficult to apply, Sonar® RTU offers the easiest application process. You just lift the lid and squirt the herbicide into the water, so it takes just a few minutes to treat your entire pond. It is important to note that you only apply half of the total dose that first day. You will want to return 21 days and 42 days later to dispense the rest of the product.


Again, the type of Sonar® you use will depend on the types of weeds you are trying to kill. No matter which type of Sonar® you select, it is important to read and follow the dosing and application directions carefully, especially if your pond is stocked with fish. In general, it’s best to apply pond chemicals in the morning on a sunny day with light wind conditions.


Step Three – Weed Removal

Eventually, the weeds will turn white and then brown, which indicates the plants have died and can be removed. You can use a pond tool such as a pond rake or skimmer to remove the dead weeds. It is important to remove as many of the plants as possible. Otherwise, they will sink to the bottom and add to your sludge layer.


If you don’t wish to use an herbicide or pond chemicals, you can remove live pond weeds from your pond. The trick with mechanical removal is to ensure that you remove all of the weeds and any root systems they might have. Even just a bit of debris can allow weeds to grow out of control again and fairly quickly if the conditions are right. If you pull live weeds out of your pond, bag them up and dispose of them carefully, away from your pond.


Preventing Pond Weeds

Once you’ve mitigated your pond weed problems, it’s time to think about prevention. Pond weeds thrive in low-oxygen environments, so adding an aeration system to your pond can go a long way toward preventing weed growth.


Additionally, runoff from irrigation and large rain events also can accelerate the growth of weeds and algae, so adding a buffer of beneficial plants can help prevent some runoff from ending up in your pond. It’s also wise to leave a buffer of grass around your pond that is not treated with fertilizers. You also could switch to fertilizers without nitrogen and phosphorus, which can cause many problems if they enter your pond ecosystem.


Using beneficial bacteria treatments also can help maintain good water quality. These bacteria consume excess nutrients in your pond and can help prevent the rapid accumulation of floating green organic matter as well as some weeds. These bacteria treatments are all-natural and easy-to-apply and can prevent many common pond issues.


At Healthy Ponds, we can provide you with products to help with just about any pond issue. In addition to the Sonar® herbicides, we also have pond chemicals to help mitigate issues with pond algae as well as natural beneficial bacteria products that can help prevent many common pond problems. If you have any questions about our pond treatment products, don’t hesitate to contact us at any time.

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Why Choose to Autoship?
  • Automatically re-order your favorite products on your schedule.
  • Easily change the products or shipping date for your upcoming Scheduled Orders.
  • Pause or cancel any time.