My copy of "Gardens Illustrated" for April '04 has just arrived and in it I
noticed that Nigel Colborn writing as "Mole" comments that:
"The threatened ban on barley straw as an agent for clearing algae from
ponds appears to be in place. Health and Safety officials have now ruled
that it is illegal to sell barley straw for this purpose under the European
Union ruling that insists that all 'biocidal' roducts be registered."

Precisely how is barley straw used to clear algae and why is it supposed to
be effective, and IS it effective?