My 3 year old dugout pond seems to be increasing the rate at which it grows algae. The algae only covers about 5% of the surface, but it seems to be getting worse each year so I’m wondering what you all think.

We dug it 3 years ago. It is a 0.15 acre dugout in perfect clay that is roughly a circle. One side is about 5:1 slope for swimming and the other sides are about 2:1. It gets about 15 feet deep. It is in the center of a 5 acre meadow that is almost perfectly flat. There is no agricultural land that would drain into it. It stays full from runoff from the local meadow and from water I collect from the roof of my cabin. There is almost no outflow of water. We also have bottom aeration. The first and second summer I ran it 24/7. This summer I ran it on a timer 12 hours a day to save some electricity cost. We are in the North East.

The pond was initially completed in the fall and filled up in 6 months over the winter. The first summer it was just “a big clay bowl” full of clear water, with nothing visible growing in it. The second summer some rushes started to grow around the edge but not much else. This summer we got more rushes and started to get some algae. I assumed this was from the build up of nutrients in the water over time (no real outflow), so in June I decided to put in pond dye. The algae kept growing so in late August I started to put in “beneficial bacteria”. The algae has continued to grow since then.

The algae is ok right now, covering maybe 5% of the surface. I am pretty diligent about manually removing it. My concern is the rate at which the algae has been increasing over the years, and what next year might look like. I’m wondering if you all have any suggestions. What do you think of this? Would running my aeration 24/7 vs 12/7 help? Are there other things I can do to decrease the rate of algae growth? Or perhaps 5% coverage is normal and it shouldn’t go much higher?

What do you think?