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Duckweed Again


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Hey all, I’ve been losing a battle to duckweed for a while, looking to get something that eats it to tip the odds in my favor, any ideas, preferably something that is peaceful in a community but if necessary I’m prepared to go more extreme…

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In my case I found that mollies eat duckweed, I read some articles about it as well and some fish that are omnivores will eat duckweed when they have chance. Common fish that will eat duckweed are carp or goldfish but those aren't really community fish.

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Call me the voice of reason, or dissenting opinion, or whatever. But why not manual removal? I've cleared a bunch of my tanks of duckweek in the past month. I use one or more of 3 tools:

  • plain old fish net
  • iphone sized pieces of plastic mesh, like what's used for embroidery
  • a small rigid or semi-rigid fish net, similar to the coop net but smaller finer mesh and wire that is more... well, rigid. 

I usually tackle this over 2-3 days: The first go uses the fish net to remove as much duckweed as I can, easily. Repeat on day 2, after everything has settled, and the duckweek collects in its usual places. When 99% of it is removed, I use the tiny dip net to collect the individual pieces left over. Monitor for a couple days, and collect the 1s and 2s that escaped in the first procedures. Check weekly after that, and remove anything that pops up. 

The small rigid fish net is hard to find. If I didn't have it, I'd make one out of the plastic mesh and tiny zip ties. 

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Have anything that can give you some good surface aggitation? My nephew's tank has a waterfall effect tank (it's small 5 gallons) he CANNOT keep Duckweed (or any other floater) alive (and he wants to). I have also found decent surface aggitation kills most floaters. 

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On 4/18/2023 at 2:03 PM, Lennie said:

Mystery snails eat it as well. Mine did not make much difference but I feed him heavily. They like eating other floating plants and their roots too tho.

@Guppysnail may confirm I guess

My mystery snail children torment me as I’m sure human children must torment their parents. In tanks I want mass floating duckweed they consume it until it’s gone ignoring all other food. In tanks I want duckweed gone they ignore it and have been spotted napping in food dishes waiting on yummies. 🤪

Edit to add. My guppies were the only consistent duckweed consumers. 

Edited by Guppysnail
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@DiscusLover I’ve heard that as well, it’s what I’m leaning towards 

@Lennie the mystery snails I can confirm I have seen them eat it, but it’s probably too far gone to attempt that option lol

@TOtrees over the years I’ve tried a number of things, craft mesh and a net work the best for me as a source of manual removal, however, one of my tanks just hatched a very small rarer fish I’ve been trying to breed for a while. I noticed the fry attach themselves to duckweed strands and sit all day. I don’t have a problem with the duckweed being in the tank except recently in the same tank it’s thrown something out of balance. Also it’s almost impossible to remove it without also accidentally missing and discarding this fish fry which I’ve only successfully bred once so my thought was if I could add something to eat it and leave the rest of the tank be I think it might be a viable option.

@xXInkedPhoenixX I have on some of my other tanks the large tidals which really stirs the surface up and it still grows like crazy

@Guppysnail I wish I had that issue regarding the snails eating it fast. 

 

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On 4/18/2023 at 11:17 AM, CJs Aquatics said:

the surface up

This is where my nephew's tank and my experience has been different- just surface doesn't really work, what worked was when it's pouring/falling, it hits the floaters and they get dunked and dunked and dunked until they die. Takes some time but it seems to work for us. 

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On 4/18/2023 at 9:05 PM, xXInkedPhoenixX said:

Have anything that can give you some good surface aggitation? My nephew's tank has a waterfall effect tank (it's small 5 gallons) he CANNOT keep Duckweed (or any other floater) alive (and he wants to). I have also found decent surface aggitation kills most floaters. 

In my 29g, duckweed didnt mind being submerged for a week or even longer lol. Waterfall HOB effect or splashing water over them def didnt work for me.

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Manual removal is a must.  Even if you use another method, a single little plant left will re-populate, so you have to be very on top of it.  Hydrogen peroxide treatment (usually used for algae) is quite hard on other floaters.  I have no duckweed so I can't confirm it kills duckweed.  You can look up instructions, generally they are:

- turn off filter and lights.

- dose 1 ml / gallon of 3% hydrogen peroxide

- turn the lights and filter back on after 40 min

 

This is plant, shirmp and snail safe in the treatments I have done but it is hard on other floating plants (frogbit, salvinia, red root floaters) as well as delicate leaved plants (elodea densa, some val varieties, wisteria, etc).  If it does work to kill duckweed, I'd repeat it weekly.

Hydrogen peroxide breaks down to water plus oxygen so no need for a water change after.  You'll notice everything pearling with the extra oxygen.  If you have any algae you want to treat, be sure to treat it as directly as possible with the peroxide.

 

Good luck with it!

Edited by CanadaAmanda
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If manual removal isn't an option bc of tiny fry attaching to the duckweeds, wouldn't adding mollies or any other fish capable of eating the duckweed be problematic? 

I had duckweed in a tank that had lots of cherry shrimp. A lot of shimplets came out with the duckweed when I removed it. To save them, I half filled a shallow white plastic storage bin with tank water, and floated the removed duckweed in that. Then I was able to use my fingers to scoop/remove the duckweed from the bin, in a manner that allowed the shrimplets time to jump ship and stay in the water, then when the duckweed was almost gone from the bin I turkey baster'd the shrimplets out and back into their tank. 

My point is where there is a will there is a way. 

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@TOtrees I completely agree with you manual removal is a must and love the idea of the tub I will try that today. 
 

@Sora I blended it once before and re- fed it, it does work it’s just a bit of a process, not too bad, never tried the blocks though that might be worth looking into

@MattyM I’m not familiar with “the duckweed destroyer, I’ll look that up thank you 

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On 4/19/2023 at 9:37 AM, Sora said:

Ive heard that if you blend up duckweed, fish will eat it. maybe even freeze in blocks. I dont have duckweed just heard this somewhere! gl 🙂

Marks Shrimp Tanks has a youtube where he freezes a bunch, then blends it with bee pollen it into shrimp food https://youtu.be/Fi8QMQlJq3o. As a born critic, I have to wonder, a) when the shrimps are eating it at the end of the video, are they just shoving the blended duckweed particles out of the way to get to the pollen, and b) can any of the duckweed bits that are released when it goes back into the tank as food grow again? Ie we've all seen (at least those of us who have duckweed) that it can readily grow from the smallest fragments, and it certainly tolerates freezing over the winter and comes back every spring, so I don't imagine that freezing it in your freezer is different enough to kill it off. Mind you, if you're feeding it into a tank that already has a covering of duckweek, it won't matter either way. 

Personally, I've always wished there was a way to turn the duckweed into human food (without the intermediate growing-season-only step of tossing it into the garden as fertilizer for my veggies). Like microgreens. 😛

 

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I wish I could feel your pain!  I've been trying to grow DW in a protected part of one of the community tanks for more than a year.  The Angelfish and Silver Dollars eat it faster tan it can reproduce.

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Question for the thread, I’ve heard people say duckweed although annoying is like natures test strip and can tell you a lot about your tank based on its color, how rapidly it spreads, how long the roots are etc. can anyone elaborate on how to read duckweed? at this point I might as well learn that language😅

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I'm not sure how to read duckweed.  :classic_laugh:  But what's growing in my tanks and porch pond is bright green and grows fast!  I use a little stainless steel strainer with a handle to manage it . :classic_cool:

20230424_134210.jpg

20230424_134214.jpg

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On 4/26/2023 at 6:57 AM, Matt B said:

I'm not sure how to read duckweed.  :classic_laugh:  But what's growing in my tanks and porch pond is bright green and grows fast!  I use a little stainless steel strainer with a handle to manage it . :classic_cool:

20230424_134210.jpg

20230424_134214.jpg

Lovely pond! What's the stocking? 

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On 4/24/2023 at 1:09 AM, CJs Aquatics said:

Question for the thread, I’ve heard people say duckweed although annoying is like natures test strip and can tell you a lot about your tank based on its color, how rapidly it spreads, how long the roots are etc. can anyone elaborate on how to read duckweed? at this point I might as well learn that language😅

I would say this is a relative thing. If you haven't been monitoring anything, and all you see is a snapshot, it won't be that useful. But if you are able to compare something between 2 or more tanks, or in one tank over a period of time, then perhaps yes you can make inferences. 

I would also say that if you know enough about your tanks and your plants to be able to detect a change based on duckweed appearance, you probably know enough to already know what's going on, or at least expect it. Example: in one of my tanks, duckweed went from aggressively colonizing every square inch of the surface (except where the sponge filter bubbles come up), to appearing half dead, grey/brown, smaller leaves, some openings, etc. I saw this about a week after one of the cfl bulbs over the tank burnt out. Which I already knew about. Did the duckweed tell me anything? Sure. Did it tell me anything I didn't already know? Not really. 

I suppose that if you have an outdoor pond, that you aren't interacting with daily (eg I often let my pond buckets go for weeks with no changes, no food, no nothing), and one day you see that all the duckweek is dying, then perhaps in the situation it might be the alert that causes you to look more closely and see what's up. But, even in that situation, dw doesn't die overnight so you're probably seeing a sign of something that began many days or even weeks ago.

My 2c, but I'm sure there will be other thoughts.

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On 4/18/2023 at 2:01 PM, DiscusLover said:

In my case I found that mollies eat duckweed, I read some articles about it as well and some fish that are omnivores will eat duckweed when they have chance. Common fish that will eat duckweed are carp or goldfish but those aren't really community fish.

Depending on the type of goldfish you get does good in a community tank 
look on you tube or goggle on it, It's pretty interesting to check out.

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On 4/18/2023 at 2:05 PM, xXInkedPhoenixX said:

Have anything that can give you some good surface aggitation? My nephew's tank has a waterfall effect tank (it's small 5 gallons) he CANNOT keep Duckweed (or any other floater) alive (and he wants to). I have also found decent surface aggitation kills most floaters. 

That's probably why I can't grow any But I Think I can fix where I can have both 
& have the floaters blocked off from the top 3 inches B-low the water line so 
they stay at 1 end of a 75 gal & the 2-power heads I have on a ugf won't bother 
the floaters, I have plenty of sponge 2 inches thick I can cut to fit 1 end of the tank.

Better yet get a long but small basket & start your floaters in it & as they grow 
have you a goldfish pond or even a grass carp in a rubber 110 gal pond wild 
caught fish will eat duckweed it's like candy to them.

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