Sounds like you have a build up of excess nutrients over the years and a strain of algae is taking advantage of those nutrients.
Once nutrients get into a pond (via water running in, added feed or fertilizer, etc) the only ways it gets back out of the pond is by removing fish or removing organic matter (like muck or plants or filamentous algae) or water flowing through and out the overflow.
So ponds tend to, over years of accumulation, get nutrient rich. Then something in nature comes along to take advantage of those nutrients. Unwanted excessive plants or excess algae are symptoms of those excess nutrients.
That is the easy part of the explanation. Curing it? That gets more complex and I will leave that to someone who actually knows.
Last edited by snrub; 03/26/18 04:36 PM.
