"Robert wrote in message ...
I have a small pond I keep for frogs and wildlife.
Each year it gets covered with a thick layer of duckweed that causes the
water to become dark and evil smelling.

It is not the cause, that's something else, and I would think it may be a
thick layer of detritius that needs cleaning out. This is in effect over
fertilizing the water causing the Dw to grow fast and thick and the water to
go stagnant. It's a problem with wildlife ponds because the muck at the
bottom contains lots of living things you want.
I've never understood where it got it's name 'cause I've never seen a Duck
eat any. :-)


I asked my local fish and pond centre for some magic powder, but they said
all you can do is scoop it out.

Correct, there is nothing out there to touch this weed that will not kill
the pond too. Get a net and use it at least weekly, I use mine almost every
time I go out to my pond in the summer, yes, daily.
In the winter it sinks only to pop back up in the spring.

This is plainly ridiculous as it grows faster than I can scoop!

Hmmm! I doubt that, but you will never get rid of it in a planted pond, 'tis
true.

I have tried emptying the pond and fitting a new liner but blow me if it
didn't come back.

Well if you put the same plants back they would have had DW on them and it
only takes one bit. Or one bit attached to a frog/bird/net/boot......

--
Regards
Bob

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