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.

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

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

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

Thus far Duckweed 3 Me 0
Any ideas???