Hello, I inherited a pond from the previous homeowner. The pond was large, about 1200 gallons and after 5 years, we downsized to about 600 gallons due to a tragic accident algae control chemical overdose that killed all 120 Koi I had in the pond. I cried. The following year, after cleaning the pond very well and downsizing, I purchased 14 new beautiful koi. 3 did survive, but 6 years later, the rest are still around and thriving. My koi are the one of the joys of my life. Although I yet to learn about how to control the annoying algae 100%, makes the water look like pea soup, I am very very careful with avoid chemicals if at all possible.