duckweed

[Wavey Davey]

Years ago (1960's) my dad would treat our backyard pond with some chemical that took care of the duckweed. I have no idea what it was. It would last a couple of months then the duckweed would return and would have to be treated again. The pond was kind of connected to a swamp so that didn't help matters much. Sorry I can't be of more help,
but there was a way to chemically treat the water for duckweed. Skimming it off the surface sounds like a lot of work and it would probably return. Good Luck.

[Eric Wettschreck]

Copper Sulfate.

Good luck getting your hands on some, however.

[erikwells]

This weed has taken over one of my ponds. Is there something out there that can help control this problem? Any help would be appreciated, as long as I get the advice before I go out to clean up the duckweed with a pool net (pond is about 100ft wide and 175 feet long and is about 15 feet deep in center).

[Dynasty]

Why do you want it out? I think its a sign that the pond is healthy.

[erikwells]

Thanks for the responses.
Looks like I will be living with the duck weed. It just make fihing topwater hard when that stuff gets so thick. Looks like I will stick to spinners and use top water when the wind will allow. Thanks

[poncho]

Copper Sulfate works, We get it and put it in some pantyhose, tie a string to it and drag it behind out Argo in our duck marsh. It takes about a week to start showing a difference, but it does work. We get ours from a local ag supply dealer, if they don't have it in stock they might order you some. it doesn't take much.

[erikwells]

Poncho, thanks for sharing. I figuered someone on this site would know this. Thnaks again and for all the responses and have a great Fall.

[Wall-Hanger]

Be careful with copper sulfate. It depletes oxygen levels and can irritate your fish. I have seen it used to kill rough fish in small ponds.

[Wall-Hanger]

Use only small amounts

[This message has been edited by Wall-Hanger (edited 10-05-2004).]

[wastewaterguru]

The duckweed is a result of excess nutrients in the pond. The nutrients can be from natural sources.....such as decomposing vegetation, fish feces, etc....or it can be from non-natural sources...such as lawn fertilizer, agricultural chemicals, septic drainage, etc.

Long term health of the pond will require some management of any non-natural sources. Leaving cattails and native shoreline vegetation in place instead of beaches will help adsorb nutrients.

Another long term option for this pond is to add aeration (small fountain).

And one more possible long term cure is to increase the presence of medium to large leafy trees to reduce the daily UV exposure of the water surface.

Large outbreaks of duckweed cause severe dissolved oxygen swings in the pond that will have a negative or fatal effect on the fish. During the day when the algae is exposed to sunlight, it increases the oxygen content of the pond from photosynthesis. At night, the dissolved oxygen can drop dramatically from the lack of sunlight and increasing oxygen demand from the decaying algae colonies.

Copper Sulfate is toxic to most game species and rough fish alike. There are some newer algaecides that are less toxic and I suggest that you do some more research on possible options.

Good Luck

[erikwells]

Wastewaterguru, thanks for your educated response. I feel as though I received a biology lesson. I get the runoff from a horse pasture so I am sure thats where the excess nutrients come from. I would like the oxygen levels to remain high as well because there are fish in the pond even though it had a hard winter last year for some reason?? Thanks again for your resonse I think I will try to find a less invasive method than the copper sulphate being I do not want to kill the frogs, minnows etc.. Enjoy the fall.

[Bubbadust]

Wastewaterguru,

I assume from your name that must know a lot about water chemistry. And I must say that I was very impressed to see somebody use the term "adsorb" (as opposed to absorb)!

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Bubbadust

[wastewaterguru]

As with a lot of things....I know just enough to be dangerous.

Duckweed has been used in wastewater ponds for decades.