I haven't used barley straw, but other rec.ponders have and maybe they can
answer your question.

Gareee wrote When you are using Barley
straw, does the green turn to brown before it finally fades away? We both
noticed here today, that the pond no longer looks green, but looks a murky
dark brown.


kathy :-)
algae primer
http://hometown.aol.com/ka30p/myhomepage/garden.html