Blue Green Algae in Backyard Pond?

Asked August 18, 2019, 9:52 PM EDT


With the recent blooms of blue-green algae, I am wondering if that is what I have in my backyard pond. If so, how do I safely control it as I have Koi fish in the pond and two dogs? I am finding conflicting info online. I can easily keep the dogs away but am worried about the Koi. I tested my water today and the nitrate and phosphorus levels are at 0 and the ammonia is .25 or less. I have both a waterfall and an aerator running.

Thank you!

Douglas County Colorado

3 Responses

I'm not an expert on this issue, so I reached out to Regan Waskom, his response is below. You can contact him directly at the email or phone number listed.

Please respond to this with your email and I will send you a copy of the Fact Sheet Regan sent me on the subject.

"Sheila, See attached fact sheet – hopefully this helps. Possible to have fish kills with aggressive algae control. In a small pond, sometimes best to just sweep net the algae clumps out regularly until cooler fall weather suppressed the growth."

Reagan M. Waskom, Director

Colorado Water Institute

Colorado State University

Fort Collins, CO 80523

(970) 491-6308

Thank you for your help. My email is