Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

"Tony" wrote:

Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

I get the stuff also. I have a swimming pool skimmer and skim it off.
It tends to be more prevalent at certain times of the year, especially
the spring. Other times it recedes.
--
Pardon my spam deterrent; send email to
18,000 gallon (17'x 47'x 2-4') lily pond garden in Zone 6
Cheers, Steve Henning in Reading, PA USA

Thanks for that. The weather is turning cooler here now (east coast of
England) as the water cools off all the plants are dying back. I have tried
skimming the top of the water using nets but the spaces soon fill up again.
I was wondering if there was anything that would eat the stuff and if there
is where to get it from. Up to now we have taken out 5 or six wheelbarrows
full, good for mulching around trees but bad for pond.
"Stephen Henning" wrote in message
news
"Tony" wrote:

Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

I get the stuff also. I have a swimming pool skimmer and skim it off.
It tends to be more prevalent at certain times of the year, especially
the spring. Other times it recedes.
--
Pardon my spam deterrent; send email to
18,000 gallon (17'x 47'x 2-4') lily pond garden in Zone 6
Cheers, Steve Henning in Reading, PA USA

On Fri, 17 Oct 2008 13:33:13 EDT, "Tony"
wrote:

Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

My pond was covered in Azola. The cat tried to walk on it when chasing
a bird!

The plant died in winter and has not comeback since.

Steve

--
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JustNN. Just Neural Networks. http://www.justnn.com
EasyNN-plus. Neural Networks plus. http://www.easynn.com
SwingNN. Forecast with Neural Network. http://www.swingnn.com

I haven't read the whole thread, so this may be repetitive.

You can fill and let the pond slowly overflow. The duckweed will go
over witht he water. It does eat a lot of nutrients and shade the
water, so you will want lots of plants in the pond to compensate.

Jim

On Fri, 17 Oct 2008 13:33:13 EDT, "Tony" wrote:

Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

Hi Tony, if you have freezing weather where you are, it will usually kill
it... Koi may eat it, if there is nothing else in the pond for them to eat.
Hope for a sustain freeze this winter? ~ jan
------------
Zone 7a, SE Washington State
Ponds: www.jjspond.us

the fish wont die if you use an aerator. the fact that the azola is covering means
there is too much nutrients not being used up by the biofilter or by a veggie filter.
get a good veggie filter set up and the azolla will starve. only other way is
something like a skimmer. Ingrid

On Fri, 17 Oct 2008 13:33:13 EDT, "Tony" wrote:

Large pond has thick carpet of small rough edged duck weed type floating
plant. I think it's called azola.
It has almost completely covered pond and fish are dying
Probably oxygenators not getting light .
The question is how do I eradicate?

Phyllis and Jim wrote:

I haven't read the whole thread, so this may be repetitive.

You can fill and let the pond slowly overflow. The duckweed will go
over witht he water. It does eat a lot of nutrients and shade the
water, so you will want lots of plants in the pond to compensate.

Azola isn't the same as duckweed. I never managed to keep duckweed in my
ponds because the fish eat it. Azolla isn't as tasty.
--
derek

oops!

I tried Googling 'kill azolla'. It makes some recommendations for
Britain at www.nerc-wallingford.ac.uk/.

Jim

A hard Winter freeze inches deep will bump off the bulk of it, though it can ressurect from fragments that found their way tangled in deeper water, or spores stomped into mud.

Harsh mist spraying and netting works well enough on a smaller size pond.

If you keep the pond well topped up, cross fingers a period of heavy rain will help to flush it through an outflow

Azolla makes a useful mulch

Regards, andy
http://i93.photobucket.com/albums/l42/adavisus/
http://www.flickr.com/photos/21940871@N06/

I have exactly the same problem, except that I don't have fish. Having trawled the Web, I found a company called Cabi (www.cabi.org.uk), who have discovered, and are marketing a weevil which feeds on Azolla. It's really expensive, but apparently the only solution.
I've attached the email response from the company - my pond did show dieback in the centre during the cold weather, but despite 4cm of ice, the Azolla is definitely still there at the margins and spreading back. I understand Koi carp also eat it - you can buy it for them on Ebay!!! But my pond is too small for them and I don't want them anyway.

Here's what Mr Azolla of Cabi says:
'The Azolla you have will likely over-winter in the pond and has probably already started to take on a red tinge. Some die-back of the weed can be expected during a ‘cold-snap’ and often the Azolla will retreat to a fringe around the margins of the water body. The plant however, is surprisingly hardy and continues to grow throughout much of the year. In laboratory studies it can survive short-term (18 hours) exposure to temperatures of -2 degrees centigrade. Exposure to -4 degrees centigrade is sufficient to kill the plant. However, because of milder winters and the protected micro-climate found in ponds, it rarely experiences these conditions.

The number of weevils recommended for release represents the minimum number required to initiate a population and give control within a reasonable timeframe. This assessment is usually based on the total area of the water body, as the plant will tend to occupy the whole area before control is exerted. The best control is afforded on large continuous areas of Azolla. These favour the weevil’s biology, as it allows for a significant population to build within the mat.

Number of weevils:

The weevils are sold in two pack sizes, large and small. The large is aimed at those with larger water bodies and would normally be expected to treat approximately 50 square meters. In practice there is flexibility in the area treated as the principal is to introduce a seed population that will continue to build within the mat until a carrying capacity is reached and the matt collapses. The 2009 costs for each large pack is £397 (Inc. VAT).

Speed of kill: In practice it is difficult to say with certainty how long control will take, as this is governed by environmental factors such as: size of the infestation; number of weevils released; size (if any) of ‘natural’ weevil population; prevailing weather conditions. Typically the first indications of Azolla control are seen 8 -12 weeks after release. There is always a lag phase between weevil introduction and control. During the lag phase weevil populations need to establish and populate the Azolla mat, it is only when weevil numbers reach critical levels that control is exerted. All life stages of the weevil feed on Azolla, however it is the larvae that are the most damaging. Feeding damage is so severe that the growing tips of the plants are killed and the plants turn brown fragment and die. The first indications of successful weevil establishment is a change in plant colour from green to brown, this usually occurs in patches and open water may start to develop between them'

Good luck!