Hi Cecil, I would look at this product "Greenclean Granular Algaecide"with some caution. It is sodium carbonate peroxyhydrate 50% which is basically hydrogen peroxide and soda ash, why the caution? It is very very safe but apperars to be weak on string type algaes and chara. We have been working with it all winter in 5 gallon grow outs to get an acceptable rate of product for control.Lets just say it takes "a bunch" The manufacturer is Biosafe 888-273-3088 We retail it for $119.60 for a 50 lb pail and will be listed on our webpage if completed this week, Keep in mind one of the biproducts of Barley Straw rotting is hydrogen peroxide and a rate of 2ppm would be great if that were practical. I have had little luck with Barley but will keep toying with it,Thanks Ted