Water Fern (Azolla) is it a problem in domestic ponds?

"Davy" wrote:

I am building a 16sq m wildlife pond in Wiltshire, England and someone who
is thinning out their pond in September has offered a whole range of plants
to get me started.
Unfortunately, their pond has azolla. Is this likely to be a problem?
There are some horrific photos on the web of large ponds and ditches
completely choked with azolla. But a garden pond owner who has azolla
states that their other plants keep it down to just a very small patch. I
imagine they compete for nutrients.
I don't expect any fertiliser runoff to enter the pond but I do expect to
top it up with tapwater. I suspect that azolla is only a problem when there
is excess nutrient in the water?
Anybody with experience?

I have an 18,000 gallon (17'x 47'x 2-4') lily pond garden which is
spring fed. It filled up in 2 days so the flow is good. The spring
water's temperature is 50 F. The pond's temperature gets up to 70 F by
the middle of summer. During the winter, my pond is dormant. The
plants are safely stashed on the bottom of the pond. Each spring (the
season) the Azolla caroliniana ("Fairy Moss") has completely covered the
pond. The way I look at it is that the Azolla provides the shade that
prevents string algae from taking over. When I bring the plants up from
the bottom of the pond and set them on their shelves, I used a skimmer
net to clean most of the Azolla off the pond. I get about 50 US gallons
of the stuff and dump it on my compost pile. The rest of the summer it
doesn't come back. To control algae, besides the Azolla and later
water lilies for shade, and marginal plants for nutrient control, I use
barley straw to prevent the string algae. I do get a small growth in
the early spring and use Algae Fix to kill it before I add the fresh
bale of barley straw. I also have native minnows to control insect
larvae, bacteria to eliminate the dead algae, and oxygenator plants and
an aerator to keep the oxygen levels up. It seems to run just fine on
its own except in the spring before the lilies and marginal plants get
going and temporarily have Azolla and string algae problems.
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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

Azolla works well for removing nutrients and you can always use a net to
remove surplus, COMPOST what you remove. I would NOT let it die off in
the pond in large quantities as the resulting decompostion may pollute
the water, it seems to go red before it dies off and at that point I'd
remove all that you can.
In my fish pond I use a the jet from a hosepipe to wash the azolla
toward my skimmer/outflowing stream.
In my heavily planted wildlife it doesnt prosper nor does duckweed. In
my plant and lily ponds it hasnt done well this year but duckweed is
doing ok.




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sean mckinney