Ponds add a unique mood to a garden, both relaxing and enticing, and although they can often be left undisturbed for long periods of time, occasional maintenance is a necessity. A natural pond, one with aquatic and bog plants as well as fish, can be set up for minimum maintenance, but watching for problems and correcting them quickly will help to preserve both the health of fish and plants and the attractiveness of your pond.
Check the water level on your pond every week or so, and add more if needed to bring the level back up to maximum. Low water levels can damage plants and reduce the amount of oxygen available to fish. Top off your pond with chlorine-free water.
Check the pH of the water occasionally, making sure it stays between 6.8 and 7.8.
Limit the number of fish in the pond to 1 inch of fish length for every 10 gallons of water. Remember that fish grow, so consider the eventual size of each fish you introduce into the pond. If there are too many fish, their wastes will produce excess ammonia, which is toxic.
Feed only the amount of food needed for the number of fish you have. Excess food will foul the water by rotting and reducing the amount of oxygen available.
Stock the pond with enough floating plants to cover about two-thirds of the surface. This helps to reduce the growth of algae. Some algae is normal and beneficial, but green water is unsightly and unhealthy for fish.
Adding other plants, both rooted specimens such as water lilies and marginal bog plants, helps to oxygenate the water and reduce the amount of ammonia and nitrite dissolved in it.
Remove most leaves that drop into the pond with a small-mesh net before they have a chance to sink to the bottom and decay. Excess organic matter will make the pond more acidic and reduce oxygen levels. If you have overhanging trees, consider covering the pond with netting in autumn to catch the falling leaves before they hit the water.
Prepare for winter by scooping excess organic matter out of the pond bottom, cutting dead leaves off the plants and making sure a small area of the pond will stay ice-free if you have hardy fish. Where winters are severe, small heaters can be purchased for this purpose, or, in mild winter areas, you can break up ice when it forms.