Consider stocking your backyard pond with native fish. They are fun to watch and help keep the pond free of unwanted insects. Most small ponds will warm up quickly in the summer, so make sure you stock with fish that can tolerate elevated temperatures.
You'll also need scavengers, such as aquatic snails and tadpoles, to help control algae. In cold climates, a heater may be necessary for fish to survive the winter. However, this uses a significant amount of electricity and, in most cases, probably is not justified. A better option may be to set up an indoor aquarium in which to overwinter fish and plants.
Backyard Pond Maintenance
Algae is a common problem in many newly established ponds. The water often becomes an unsightly green after a few days. While your first instinct is to drain the pond and start over, this only prolongs the problem. Once a pond is "balanced," algae usually are kept at an acceptable level. A balanced pond is one in which the nutrients are at the appropriate level for the plants present. Excess nutrients and light are needed for algae. Reducing the nutrients and decreasing the amount of light entering the water will help reduce algae. Floating plants or those with broad leaves such as water lilies will help reduce the amount of light available for algae and compete for available nutrients. Scavengers such as snails will help clean up wastes from the bottom of the pond.
Pond filters can help reduce algae, but require maintenance. Filters need to be cleaned frequently if algae is a problem. Chemicals can also be used to control algae. Use cautiously as they can be toxic to other plants and aquatic life. The need for algaecides should decrease as plants become established.
Excessive plant growth, especially of free-floating plants, may be a problem. Periodically skim off excess growth of duckweed, water lettuce, and other floating plants. Monthly, prune dying plant material. Clean out some of the decaying plant material that has accumulated in the bottom of the pond in the spring. Remember: a natural pond is not a swimming pool and too much cleaning can do more harm than good.
Courtesy of the US Department of Agriculture, Natural Resources Conservation Service.