How to Remove Duckweed From Aquarium

If you have an aquarium, then you’ve probably seen Duckweed floating on top. Unfortunately, Duckweed is a small plant that can increase and become out of control. If left alone, it will take over your entire tank and kill off all the beneficial bacteria in the substrate.

How to Remove Duckweed From Aquarium

This blog post would be interesting to read because I like having fish in my house, and it seems like something that could happen if I didn’t care for my tank properly. So, this article is for you. You will learn how to remove duckweed from aquarium with just one simple trick!

Step to Follow on How to Remove Duckweed From Aquarium

Step One: Determine

The first thing to do is determine whether or not you even have Duckweed in your aquarium.  One excellent way to do this is by turning off the lights and doing a white background check with a flashlight. Sometimes, Duckweed can blend in with the gravel floor so well that the only way to tell for sure is by doing this little trick.

Turn on Light and Check

If you do see any green floating around your tank, note how many leaves there are and what they look like. Do a little research to find out what kind of Duckweed this is and how fast it spreads. If you do not see any green floating around your tank, that doesn’t mean that there isn’t any.

Step Two: Pick Up All Substrate

Before you can do anything else, you need to get rid of all the Duckweed at once.  The best way to do this is by picking up all the substrate in your tank and removing it. If you cannot do this for some reason, maybe because there is no light in the room, you will need to get creative.

Use your siphon to suck out all the Duckweed by creating suction with the end of the hose and putting it near the Duckweed.  If you do not have a siphon or broken, you can try using your net to scoop out all the Duckweed. Use medium-sized nets instead of large ones to get all the little pieces in addition to larger pieces.

Step Three: Remove All Water From the Tank

After you have picked up all of the Duckweed and substrate, it is time to empty out all the water in your tank.  If there was a lot of Duckweed in your tank, this step might take several hours or even days, depending on how large your tank is. You will need clean tap water to replace the old water in the tank.

Remove All Water From the Tank

Once you have siphoned or scooped out all of the old water, add in clean tap water and stir it up a bit with a clean object so that the dirt settles to the bottom. You mustn’t add in too much tap water at once, or your tank may end up with a lot of extra water and not enough Duckweed.

Step Four: Remove Duckweed From the Water

After you have siphoned or scooped out all of the old water and put it in clean tap water, it is time to remove the Duckweed.  Take your net and dip it into your aquarium while scooping up Duckweed. If you cannot get any more out this way, take a spoon and scrape the Duckweed off the top of the water.

After you have removed all the Duckweed, it is time to take the tank lid off and let all of the water evaporate. Just leave it alone for a week or so until all of the water has evaporated. Once it has, put your substrate and plants back inside and refill your tank with clean tap water.

Step Five: Add Back in Any Fish

Once you have refilled your aquarium with clean tap water, it is time to put all of your plants and fish back inside.  You mustn’t dump too much tap water into the tank because the filter has probably picked up a lot of the nitrates from the Duckweed.

If this happens, you will have to start the whole tank again because tap water cannot provide enough nitrates for your fish. If you want to find out more about how to remove duckweed from aquarium, keep reading.

Step Five: Spray the Duckweed

After you have successfully added back your Duckweed, it is time to spray the Duckweed with water.  This will serve two purposes. One is that it will help anchor the Duckweed so that it does not float around in the tank and become a problem again.

The other purpose is to revitalize any Duckweed that may have died while it was out of the water. Take your spray bottle, put in some clean water, then spray all the duckweed you added into the tank. Do this until all of the Duckweed is moist.

Step Seven: Add in Duckweed

After refilling your tank with fresh tap water, it is time to add back all of the Duckweed that you removed. Take the bag containing your Duckweed and pour it into the aquarium, making sure not to dump too much at once because this could kill off all of your fish.

Only put in as much Duckweed as your filter can handle. For example, if you have a small fish tank with a small filter, only put in a few strands of Duckweed to start with. These steps should help you in learning how to remove duckweed from aquarium.

Step Eight: Feed Your Fish

Once you have successfully added all of your Duckweed back into the tank, it is time to feed your fish again.  If you did not find all of the pieces of Duckweed while removing them from the tank, be sure to watch for new Duckweed in case any grew overnight.

Feed Your Fish

Only feed your fish as much as they can eat in a minute or two, and only feed them every other day so that there is enough Duckweed for the fish to eat. If you do not mind your fish eating some of the duckweed seeds on the way out, feel free to feed them as often.

Step Nine: Maintain Your Tank

Once you have successfully added all of your Duckweed back into the tank, it is time to maintain your tank again.  It would help if you did this because you had to take out some of the nitrates when removing the Duckweed, and this will give you time for them to build up again before the fish need them.

There are two ways to maintain your tank. You can use a fishless cycle or use the fish in your aquarium as the source of ammonia until all of it has been converted into nitrates and then into nitrogen gas that dissipates into the air. If you would like to learn more about doing a fishless cycle, please check out this article.

Step Ten: Maintain Your Duckweed

Once you have successfully added all of your Duckweed back into the tank, it is time to maintain your Duckweed again.  This is important because you will want to ensure that the Duckweed does not begin to grow and take over your aquarium once more.

The best way to maintain your Duckweed for this first month is to remove any Duckweed that grows outside of the tank.  When you do this, be sure to put it in a bag with fresh water and store it inside for about three weeks. After three weeks, drain the Duckweed of its dirty water and replace it with clean tap water again.

Maintain Your Duckweed

From what I’ve read, there is a water recycling system that Duckweed may naturally attach to in the wild. The water recycling system is a tree or plant that has grown in the marsh/swamp area. This will help in how to remove duckweed from aquarium.

Step Ten: Watch Your Tank

Now that you have successfully added your Duckweed back into the tank, it is time to watch your tank.  Watch for there not to be too much Duckweed in the water because this could kill off all of your fish. On the other hand, if there is too much Duckweed, remove some before it has a chance to grow out of the water.

A lot goes into getting rid of Duckweed, but with some hard work and dedication, you will be able to remove all of the Duckweed from your aquarium in a matter of a couple of days.

Frequently Asked Question

Is Duckweed Bad for Aquarium?

No, duckweed is not bad for aquariums. Duckweed has a lot of benefits and can be used to help maintain the health of your tank. It removes excess nitrates from the water and helps control algae growth by filtering out nitrogenous waste before it reaches the surface of the water.

It also provides beneficial nutrients such as protein, vitamins, minerals, and amino acids that are essential for fish health.

Do Aquarium Fish Eat Duckweed?

No, duckweed is not appropriate food for aquarium fish. Duckweed does not contain any nutrients that would be beneficial to the fish and it can even be toxic.

What Type of Fish Will Eat Duckweed?

Duckweed is a very popular and common type of aquatic plant that can be found in many different parts of the world.

Two types of fish will eat duckweed: predatory fish and non-predatory fish.

Predatory fish include largemouth bass, black crappie, channel catfish, bluegill sunfish, redear sunfish, green sunfish, largemouth catfish, and flathead catfish.

Non-predatory fish include smallmouth bass, bluegill (sunfishes), walleye (smallmouths), yellow perch (bluegills), brown bullhead minnow (yellow perches), yellow bullhead minnow (brown bullheads), fathead minnow (smallmouth), and redtail chub.

Does Duckweed Clean Water?

Duckweed is a type of aquatic plant that can clean water and remove chemicals.

There are many benefits of using duckweed to clean water like:

  • It can remove up to 99% of the pollutants, bacteria, and viruses found in contaminated water.
  • It can filter out heavy metals such as lead, mercury, arsenic, and cadmium.
  • It has the ability to trap organic waste like oil slicks or other pollutants that may enter into a body of water from land-based sources.
  • Duckweed can absorb nitrates from polluted bodies of water that may cause cancer or lead to algae blooms.

Does Duckweed Come Back Every Year?

Duckweed is a plant that grows very quickly and can reproduce by sprouting new plants from its root. It is not a weed, but it looks like one because of the leaves on its stem. Duckweed comes back every year because it has been genetically modified to have flowers that turn into seeds to spread around.

Duckweed will only come back if you have duckweed plants or water with duckweed growing in it. Otherwise, there won’t be any more Duckweed!


If you’re reading this article, the chances are that your aquarium is plagued with Duckweed. Unfortunately, duckweed can be a pain to remove from the tank, and it may take some trial and error before finding an effective solution.

The most common way people try to clean the water of these pesky plants is by using copper sulfate or potassium permanganate, both of which have toxic effects on fish if not used properly. For best results, use one teaspoon per gallon in the tank for 24 hours without adding other chemicals afterward.

You can also purchase commercially available organic products designed specifically for removing algae found around aquatic environments. Some of these products can be purchased from local pet stores or online. This blog post has given helpful advice on how to remove duckweed from aquariums.

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