Theo -
1. Supposedly it is the lignins that leach from the barley straw that provide the stimulus for algae control. Barley straw supposedly contains the highest concentrations of lignins of the straws / grasses. The leached lignins degrade in the presence of sunlight and produce substances (oxidizers) that inhibit certain types of algae.

2. Hurt anything? Probably not. It depends on how you define "hurt". I did say he was on his own on this one. I have no strong opinion pro or con. I do believe that proper amounts of hay in a pond will cause the suspended solids such as soil particles to more rapidly settle out of suspension. But on the other hand clearer water will allow more light penetration deeper into the water to probably stimulate more filamentous algae or rooted plant growth at deeper depths, especially if adequate nutrients are present. Fair amounts of decaying straw-hay will increase the Biological Oxygen Demand and contribute to the amount of dead organic materials which do contain nutrients on the bottom. Nutrients stimulate plant growth. Adding hay? As I said, He is on his own. If he tries it he can come back here and tell us how well it worked. I would like that.

I had one local guy have good algae control with barley straw and a neighbor said the filamentous algae GREW on top of his barley straw!!

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
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