Maintaining a healthy pond is all about establishing a balance between water, plants and fish. Fish produce waste that can overwhelm a pond's ecosystem. Unhealthy water leads to unhealthy fish, which can succumb to disease and die. A combination of filters, plants and proper aeration will balance your pond.
Stock your pond with the right number and size of fish. Overcrowding leads to overproduction of waste and proliferation of disease. Consult a local pond supplier to find out how many fish your pond can support. According to ABC Ponds, the proper ratio is 1 1/2 inches of fish for each 50 l. of water.
Make sure you're not overfeeding your fish. Any food that isn't eaten quickly will sink to the bottom of the pond and rot, contributing to the waste problem. If you fish are overeating, they'll produce more waste than is healthy for your pond. Feed your fish the amount of food they will consume completely in five minutes. Cut back on food in colder months, when fish are less active.
Use a mechanical filter and a biological filter. A mechanical filter strains out leaves and other debris that can sink to the bottom of the pond and rot. A biological filter uses healthy bacteria to break down fish waste and keep the water clean.
Aerate the pond. Aeration adds oxygen, which helps support healthy bacteria and keeps the pond from becoming stagnant. A fountain aerates the pond and provides a pleasant backdrop for your garden. Oxygenating plants such as parrot feather, water lettuce and water violet add oxygen to the pond and help keep the water clear.
Maintain the proper chemistry. Test your pond's chemistry at least once a month. While pH and other levels will vary naturally, aim for a pH of between 6.8 and 9 and an alkalinity level of between 100 and 300 parts per million. You can add substances to adjust the pH, but only use chemicals approved for use with live fish.