Definitely is a bit pricey.was in an LFS the other day and saw what I can only describe as time bales of barley straw (?) for controlling pond algae for £15. This seemed like extortion to me
The mode of action isn't really understood, there is some suggestion that the straw acts as a refuge and nursery for zoo plankton, these then eat your green water phyto plankton. Other people have suggested that it has to be Barley Straw and it is an allelopathic effect. Personally I'm dubious about both Barley Straw and allelopathy. My personal recipe is the same one I use for the tanks, lots of plants, including some emergents or floaters. The linked thread is well worth a read.I don't believe Barley actually works. I'm sure there is a thread some where regarding the use of EI dosing and healthy plant growth to combat algae in the pond.
Isn't it a case of once the higher plants get going, they take all the nutrients and the blanket weed and lower stuff dies?