Changing the water in a koi pond doesn’t need to be done all at once, as koi ponds rely on a balanced ecosystem supported by filtration and beneficial bacteria. Instead, partial water changes of about 10 to 20 percent every one to two weeks help maintain good water quality by removing excess nutrients, waste, and harmful chemicals. Frequent partial changes are better than infrequent large water replacements because they reduce stress on the fish and help keep water parameters stable.
It’s important to treat tap water to remove chlorine or chloramines before adding it to the pond, as these chemicals can harm koi. Monitoring water quality regularly with test kits for ammonia, nitrites, nitrates, and pH will help you know when water changes are necessary. If the pond is well-filtered and not overcrowded, water changes might be less frequent. During hot weather or when fish are feeding more, more frequent water changes can help keep the environment healthy.
