the less the better. when you do it early in the season , before it starts to take control is the best time. when you see it growing in the shallow water apply to the banks about 3 or 4 ft out. i spread it buy hand. after it has killed the algae , when it starts to return , take a paddle and just walk around the pond and stir up the shallow water. it will continue to kill it all summer long. i use 25 lbs for the whole year in a acre pond. it will kill fish eggs. thats about $3 each year for an algae free pond for 5 years now.

i only wanted to have some fun