# I kill Duckweed



## Red_Rose (Mar 18, 2007)

Both of my tanks are Walstad set ups and when I had set up my first tank back in 2007, I had no problems growing Duckweed. This plant would grow to form a thick mat on the surface but now since I've set up my other tank and re-done my betta tank, Duckweed just won't grow for me.

Why can't I grow Duckweed anymore? Is there a specific nutrient that this plant needs that my tanks may be lacking in? All of my other plants including my Hornwort is growing great but for some reason, I just cannot grow Duckweed anymore.


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## doubleott05 (Jul 20, 2005)

maybe its being out competed by other plants.... just a thought

did you change your lighting setup?

ferts change?


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## Red_Rose (Mar 18, 2007)

The lighting hasn't changed at all. I've always used a total of 20 watts of CFL for each tank and as for fertilizers, leftover food and fish wastes is what fertilizes the tank.

The two differences between when I had first set up the tank compared to now is before I tore down my betta's tank, the KH was anywhere from 17-22dKH whereas in both tanks now it's around 8-10dKH. That and both tanks have nitrates in it whereas before, there were zero nitrates. Perhaps those two things have something to do with the fact that I cannot grow Duckweed anymore?


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## aquabillpers (Apr 13, 2006)

Could it be that the light bulbs are not putting out as much energy as they did? They do need to be replaced periodically even though they look OK.

Bill


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## dapellegrini (Jan 18, 2007)

strange, though....

i know people who would pay to have this problem 

maybe you should start selling small vials of your aquarium water to those who can't seem to get rid of it...

:shock:


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## queijoman (Jun 23, 2008)

The experience that I have had with duckweed is that it will grow and multiply like an explosion until the entire top is covered, and then it will die off completely. Once it came back after a year as if by magic. , but after it's growth explosion it died off completely again. I think I agree with the nutrient theory because in my situation it may use up some key nutrient that it needs and then die off. I rarely and only lightly dose ferts.


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## SJInverts (May 26, 2009)

Unsual that you have this problem. Most people complain about not being able to get rid of it.


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## PeterE (Feb 9, 2010)

Duckweed, for me, does not grow at all where there is significant current and surface turbulence in the water. Is your filter outflow near the surface, and fast enough to cause this?


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## Red_Rose (Mar 18, 2007)

PeterE said:


> Duckweed, for me, does not grow at all where there is significant current and surface turbulence in the water. Is your filter outflow near the surface, and fast enough to cause this?


I've often wondered if that was a possible cause. I have a baffle over my HOB but the surface does move around quite a bit even though the water isn't crashing down into the tank so perhaps that's why I can't grow it well anymore. I know that Water Lettuce does not like that kind of water movement because it never lasted long in that tank.

It's funny, isn't it? I want to grow it yet others want to kill it off.


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## THHNguyen (Dec 2, 2006)

The title of this thread made me laugh out loud. Significant water movement does hinder growth. Duckweed likes to sit still.


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