Three weeks ago the allotment pond was absolutely choked with blanketweed and algae. The tadpoles were hatching but they could barely move, poor things, and it looked a disgusting foaming green mess.
Eleven days ago I put a bundle of barley straw in the pond.
Today, the water is crystal clear! I'm so impressed. Admittedly my pond is very small - I guess around one cubic metre - but I never expected it would be that effective. And the tadpoles are all grown up and loving it - you can see them chilling out all over the white rock in the picture below.
Barley straw for ponds comes in small packages wrapped in net, so all you have to do is tie a weight to it and drop it in. Blanketweed, duckweed and many algaes thrive in water where there is an excess of nitrogen, usually caused by too much organic matter decomposing in the pond. The barley straw works because as it rots it actually uses up all that excess nitrogen, and the weeds die. Some say the chemical reactions it produces also create a very low, constant solution of hydrogen peroxide (bleach) which inhibits further algae growth - this appears to still be under discussion... I'm hoping it should help my duckweed problem too with a bit more time. Hurrah!
This centuries-old all-natural multipurpose balancing treatment for ponds is not allowed in most of the EU due to 'insufficient research' - can you believe it??
My only question now is: if it's that effective in my tiny pond, will I be overdosing the water if I leave it in for the several months it will take to completely decompose?