We have a 20 year old pond with a three tier eight foot waterfall. The pond is thirty feet by sixty feet - the average depth is five feet, ten feet at the deepest. In June we had a lawn service spray weed and feed on our yard which encircles the pond. We were assured that no phosphates were used. Since that time the waterfall has been creating foam which enters the pond. Patches of foam float on the pond's surface. The sun causes the foam to diminish in size. We need to know the cause of the foam and how to get rid of it. Do we also need to have the water tested and where ?