# How to easily get rid of duckweed



## activesize

Duckweed. 

I liked Duckweed at first and thought we could get along okay. I thought, gee that's not so bad. I'll just spend a few minutes netting it out every now and then. How relaxing! Then I started removing pounds of it every few weeks from my tanks. Then, more pounds of the green demon once or twice a week. Not only that but it would take more than a few minutes and actually more like a half an hour to an hour to cull it down enough from all my tanks so that it didn't instantly spring back. To service Duckweed was the principal work that I needed to perform every few days in order for Duckweed to allow the rest of my plants to live with it. 

Now that Duckweed is gone I've gone back to enjoying life again. The irony is that I never actually needed Duckweed anyway. Duckweed go bother someone else. But how did I get rid of it?

I have perfected a simple technique for getting rid of Duckweed that is not too tedious and does not even require the removal of tank equipment. If your filter is forcing Duckweed off the surface then you will have to turn your filter off at some point during the procedure. Don't keep it off too long though. What I do is first take out all Duckweed that I can get to fairly easily in the normal way with a net. Then, I use a rectangular clear plastic tub, the type that originally came with lunch meat, and slowly skim the surface with it. The tub should be small enough to easily hold in one hand while performing the technique. The technique is to hold the tub stationary, tilt it slightly, and slowly push it down into the water. The idea is to very slowly draw the water into one of the long sides of the tub. This creates a vacuum effect on that side and all debris on the water's surface is drawn into the tub from many inches away. Duckweed magically appears from out of nowhere and goes into the tub. Then, you dump out the water from the tub into a five gallon bucket and use the tub again at a different location in the tank. Do this again and again and again until all the hidden duckweed on the surface is gone. Next, wash the tub and also your hands and arms. Dump the 5 gallon bucket if you need to. Next, you sort of agitate the plants and also remove any algae from the bottom or other surfaces that is hiding rogue pieces of duckweed. Then, you wait until that duckweed appears at the surface. Then, you just skim the duckweed off with the tub as before. Over a period of about a week keep looking for new pieces of duckweed to appear and skim them off too. Look for more rogue duckweed hiding on the bottom too. Remove those with tweezers or your favorite hand tool. Obviously, when you get new plants in put them in a bowl of water first and look for duckweed coming off before planting. 

That's it. It's not tedious if you don't attempt to do it all in one try. You do need a little patience, and a sharp eye helps. Don't get discouraged if you don't get it all the first time. Just try again the next day and the next until it's 100 percent gone.


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## NeonFlux

A great thought. I might have to try this out.  I have just barely began getting duckweed into invasive mode. Thanks for the idea!


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## Alserra

Well if I defend the benefits of Duckweed although it is tedious to be controlling Duckweed


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## Douglas Ingram

I got rid of all of my duckweed years ago. It just wasn't worth the hassle to me. I scooped out as much as possible, did the overflow trick, then had to pick out every last piece of it by hand.

Its a nice enough plant, but it just overwhelms my system so fast.


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## hornedtoad1

i've actually been wanting some duckweed, even checked on buying it, but nobody sells less than a 1/4 pound of the stuff. got some of it with the first plants, it died. darn. some came with the 2nd batch of plants last week, and that seems to be doing fine so far. there's been some hair algae growing in my 10-gal npt, a slow but steady increase, and i was hoping the duckweed would help to fight it. maybe i should reconsider that.


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## firefiend

hornedtoad1 said:


> i've actually been wanting some duckweed, even checked on buying it, but nobody sells less than a 1/4 pound of the stuff. got some of it with the first plants, it died. darn. some came with the 2nd batch of plants last week, and that seems to be doing fine so far. there's been some hair algae growing in my 10-gal npt, a slow but steady increase, and i was hoping the duckweed would help to fight it. maybe i should reconsider that.


The Tropical Hunt in Portland gives it away... I'd keep checking the LFS's and maybe you'll find one that does the same.


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## activesize

hornedtoad1 said:


> i've actually been wanting some duckweed, even checked on buying it, but nobody sells less than a 1/4 pound of the stuff. got some of it with the first plants, it died. darn. some came with the 2nd batch of plants last week, and that seems to be doing fine so far. there's been some hair algae growing in my 10-gal npt, a slow but steady increase, and i was hoping the duckweed would help to fight it. maybe i should reconsider that.


If your duckweed actually died then it just goes to show how every tank is different. You may ultimately like duckweed in your setup based on how it performs and your personal preferences. I was also plagued with string algae and I can only offer my personal observation that full-on thick duckweed in my 125 gallon, 55 gallon, and 32 gallon tanks all plumbed together did not lessen or control the string algae at all. I think the main thing that really destroyed all types of algae in my 125 gallon was massive growth of anacharis, hygrophila species, wisteria, and indian fern after the duckweed was removed. String algae in the other tanks were greatly lessened by plant growth and also other measures I took later, including vacuuming excess mulm, glass taping, better clean-up crew, and smarter water circulation, and not by duckweed.


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## sierramists1

Love my duckweed but it's starting to take over. I think now's the time I'll try this! Thanks!


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## hornedtoad1

activesize said:


> If your duckweed actually died then it just goes to show how every tank is different. You may ultimately like duckweed in your setup based on how it performs and your personal preferences. I was also plagued with string algae and I can only offer my personal observation that full-on thick duckweed in my 125 gallon, 55 gallon, and 32 gallon tanks all plumbed together did not lessen or control the string algae at all. I think the main thing that really destroyed all types of algae in my 125 gallon was massive growth of anacharis, hygrophila species, wisteria, and indian fern after the duckweed was removed. String algae in the other tanks were greatly lessened by plant growth and also other measures I took later, including vacuuming excess mulm, glass taping, better clean-up crew, and smarter water circulation, and not by duckweed.


this is really good info for me, thanks. the tank (10-gal) is about 2 months now, with bacopa minnieri and b.australis, sag. subulata, java moss, ech.tenellus, crypt. parva, floating frogbit, and anubias barteri v. nana. most of them are doing pretty well except the ech. the last couple of weeks there's been string/tuft algae that is spreading slowly; it's even on the anubias. i've taped the substrate on the window side--flat green algae was growing on the glass by the s/s there, and there's tuft algae on all of the glass, actually. the glass gets cleaned a lot. i changed out the 23w cfl for a 13w one; and got 4 floating frogbits a week or so ago. everything i can find to do in dr walstad's book. there are lots of snails, and the platies pick at the algae.
sorry to hear that the duckweed doesn't help that much with the algae, i was hoping it would.
i'm not sure what you mean by "smarter water circulation"; i've got an airstone with moderate air flow, placed pretty much in the center of the tank.
i was wondering whether more babies shouldn't be removed; they are small and wouldn't crank out much mulm, but there are a lot of them.


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## activesize

hornedtoad1 said:


> this is really good info for me, thanks. the tank (10-gal) is about 2 months now, with bacopa minnieri and b.australis, sag. subulata, java moss, ech.tenellus, crypt. parva, floating frogbit, and anubias barteri v. nana. most of them are doing pretty well except the ech. the last couple of weeks there's been string/tuft algae that is spreading slowly; it's even on the anubias. i've taped the substrate on the window side--flat green algae was growing on the glass by the s/s there, and there's tuft algae on all of the glass, actually. the glass gets cleaned a lot. i changed out the 23w cfl for a 13w one; and got 4 floating frogbits a week or so ago. everything i can find to do in dr walstad's book. there are lots of snails, and the platies pick at the algae.
> sorry to hear that the duckweed doesn't help that much with the algae, i was hoping it would.
> i'm not sure what you mean by "smarter water circulation"; i've got an airstone with moderate air flow, placed pretty much in the center of the tank.
> i was wondering whether more babies shouldn't be removed; they are small and wouldn't crank out much mulm, but there are a lot of them.


It sounds like you're doing pretty well since your plants are growing. My pygmy chain sword just sat there. At first, I didn't have enough light for it. Then, when I got more light then I think crowding became a problem. I've had better luck with aquatic clover. Perhaps your algae problems will get better. Perhaps they will never go away because they're inherent in your choice of setup, water parameters, maintenance and feeding habits, etc.

By "smarter water circulation" I was just referring to my own case. I'm trying for more water circulation then is normally used for a 55 gallon planted tank, with lace rock islands with no soil underneath the islands. I use a Koralia circulation pump and the vertical position of the pump seems to have a lot to do with the way that the algae associates with the rocks. At a lower pump position just above the rocks I get more string algae everywhere. At a higher pump position more than half way up the tank the algae tuffs up more and doesn't form long strings hardly at all.

My basic problem with Duckweed is that it tended to become so thick that it blocked the light from above and hurt or killed a lot of my other plants. Not only did the plants below not get quite enough light, but they were not able to keep up with the diatom and/or algae growth on their leaves. I couldn't keep up with it either. A lot of the time In my 125 gallon I couldn't even see the plants due to constant diatom build up on the front glass. Actually, a better filter would've helped me a lot but since I sent Duckweed packing then my other plants grew and I don't need that level of filtration. I still use a small filter, which I think smooths things over in the long run, but it's a pleasure not to have to rely on filtration pumps anymore.


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## farrenator

If you know someone with a Rainbowfish tank you can give them duckweed. My rainbows love to eat the stuff. I used to get some for free from my LFS and it never lasted more than a few hours. Rainbows wouldn't work for an overgrown tank but they would probably knock out any stragglers.



activesize said:


> It sounds like you're doing pretty well since your plants are growing. My pygmy chain sword just sat there. At first, I didn't have enough light for it. Then, when I got more light then I think crowding became a problem. I've had better luck with aquatic clover. Perhaps your algae problems will get better. Perhaps they will never go away because they're inherent in your choice of setup, water parameters, maintenance and feeding habits, etc.
> 
> By "smarter water circulation" I was just referring to my own case. I'm trying for more water circulation then is normally used for a 55 gallon planted tank, with lace rock islands with no soil underneath the islands. I use a Koralia circulation pump and the vertical position of the pump seems to have a lot to do with the way that the algae associates with the rocks. At a lower pump position just above the rocks I get more string algae everywhere. At a higher pump position more than half way up the tank the algae tuffs up more and doesn't form long strings hardly at all.
> 
> My basic problem with Duckweed is that it tended to become so thick that it blocked the light from above and hurt or killed a lot of my other plants. Not only did the plants below not get quite enough light, but they were not able to keep up with the diatom and/or algae growth on their leaves. I couldn't keep up with it either. A lot of the time In my 125 gallon I couldn't even see the plants due to constant diatom build up on the front glass. Actually, a better filter would've helped me a lot but since I sent Duckweed packing then my other plants grew and I don't need that level of filtration. I still use a small filter, which I think smooths things over in the long run, but it's a pleasure not to have to rely on filtration pumps anymore.


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## activesize

farrenator said:


> If you know someone with a Rainbowfish tank you can give them duckweed. My rainbows love to eat the stuff. I used to get some for free from my LFS and it never lasted more than a few hours. Rainbows wouldn't work for an overgrown tank but they would probably knock out any stragglers.


Thanks, that's good to know. I was sorely tempted to bid on some Misool rainbows over the weekend because they look incredible. Maybe Duckweed could justify it's existence if you had a small, dedicated Duckweed tank, or pond, and stock it with flagfish, or a few goldfish. Then, just harvest Duckweed basically as a food source for rainbows in your main tank. I also read somewhere that other fish may eat dried Duckweed just like flakes, and it's very nutritious, but I never tried it. I guess I thought it was too good to be true.


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