Pond Algae

Asked April 20, 2016, 12:45 PM EDT

We have a 2 acre pond that is currently growing algae on the surface, plumes under the water, and another stringy "plant like" plume growing from the bottom in the shallow areas. How do I control or eliminate the algae? It started a year or two ago and is getting worse. We have bass in the pond and it is used for swimming in the summer.

Lane County Oregon pond and water gardens algae

3 Responses

Best thing to do is find the source of the excess nutrients. Particularly nitrogen or phosphorus. Is it fertilizer runoff? Too many fishes? Too much feed being given to the fishes? What's the root cause? Once you get that mastered you do have some options highlighted here:


I'd focus on prevention and elimination of nutrient sources, then follow with chemicals to remove the problem. Grass carp and dye products are listed, but aren't effective. Also note that copper products are highly toxic to trout and should not be selected if trout are downstream or in the pond.

Thank you for your reply. The pond is in a wooded area. The water is replenished every year from run off from the hill and forest behind it. We did some extensive logging a couple of years ago. Is it possible the nutrient source is the decaying logging debris and some of the fallen branches surrounding the pond (some are in the water)? If I treat the water with chemical and copper products, are the fish (small mouth bass) still safe to eat, or should we wait a period of time? Thank you for your help.

Usually that's not a big cause. I'm thinking more along the lines of fertilizer that might've been applied or possibly a failing septic system?

Looking at our pesticide handbook diquat has a 3 day interval for waters used for drinking, but neither has a restriction at labeled rates for fishing or swimming.