Product: Water Treatments - Barley
Barley straw is kind of a unique treatment. It comes mini hay bales, wrapped in netting, pellets or liquid extract. Some people just swear by barley as a way to keep down and prevent algae from growing.
If you have a lot of algae already, adding barley is probably a little too late so you want to clean that up, use your traditional algae control products, and then add barley once you've got it cleared up.