Louis, I expect that the dying algae is contributing to your nutrient load. Once it gets started, it pretty well feeds on itself. Spraying a heavy infestation only contributes more nutrients as it dies.

I know nothing about cold water algae or it's survival. With it being spring fed, can you even drain it?

Hopefully Kelly Duffie will see this and chime in.

It's not about the fish. It's about the pond. Take care of the pond and the fish will be fine. PB subscriber since before it was in color.

Without a sense of urgency, Nothing ever gets done.

Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley Rancher and Farmer Muleshoe Texas 1892-1985 RIP