The average pond maintenance cost is $2,000. But how much you pay to take care of your pond depends on multiple factors, such as the size of the pond and whether fish live in it. Your area's climate also affects the overall maintenance cost, as you may need to winterize your pond to protect it and any aquatic life in it during the colder months.

A koi pond should be at least 5 feet deep to keep the fish healthy and ensure they don’t freeze in winter. Koi fish are also known for growing large, so the more room you have, the better. A larger koi pond size will allow the fish to grow bigger than a smaller one will, and the more fish you have, the bigger the pond you’ll need. Learn how to build a pond in your backyard to ensure it remains functional and aesthetically pleasing for a long time.

How many fish can call your pond home depends on the volume of the pond and the fish size. Your pond's filtration system also influences the number of fish that will thrive in a pond. A general rule of thumb is to have 1 inch of fish for every square foot in a pond that's 2 feet deep. Another rule of thumb you can follow is to have one koi fish for every 200 gallons of water or two goldfish for every 200 gallons.

Though there are a lot of factors that go into caring for a koi pond, the most important maintenance you can do is frequent water checks using a koi pond test strip that checks the water for dangerous conditions.  In addition to regular pond maintenance costs, you’ll also need to winterize your koi pond if you live in a colder area.