The best way to stop the growth of “this” on the pond surface is to stop dumping all of the fertilizer and other chemicals on the grass that then wash into the pond. As far as the fish and other life that lives in the pond are concerned, the pond is dying. We are killing it. Would you want to swim in it?
I saw a snapping turtle leave the pond the other day and head down towards Plum Creek. It might have thought that it was time to find another home.