Controlling Algae in the Garden Pond

Controlling Algae in the Garden Pond

Algae are ubiquitous non-flowering plant forms that can be found in nearly every biome on the planet. Believed to have been the first life form on earth, the emergence and success of algal species paved the way for the evolution of other life forms. Ranging in type from microscopic single cells to long stands of kelp that form massive beds in the oceans, aquatic algae are the very heart of the food chain. Photosynthetic algae account for more than half of the earth’s carbon fixation and its consequent release of oxygen. Algae maintain global oxygen levels at the optimum 21% of atmospheric gases. In the backyard garden pond, however, an abundance of this critical species can be an unsightly nuisance.

Algae reproduce by spores which become airborne and are disseminated by wind. The spores inevitably come to rest in the garden pond to begin their life cycles in their new environment. A few spores can quickly become an active population causing ‘green water’ and an abundance of stringy, filamentous growth. Fish ponds supply an endless source of nutrients for the proliferating algae. This food supply combined with photosynthesis provide optimum conditions for algal growth. Controlling algae populations is often necessary to keep the pond balanced, healthy, and clear.

The Balanced Pond

The garden pond, by its nature, is an artificial environment and establishing an ideal natural balance of plants, fish and scavengers occurs over time. A combination of biological, physical and chemical factors contribute to this balance. The rapid proliferation of one species over another, still water and pollution are common conditions that affect the natural balance. Pond keepers can accelerate naturalization of the garden pond with planning and good management.

Aquatic plants, such as lilies and floating plants and submerged oxygenating species, provide adequate shade and reduce the proliferation of algae and should cover approximately 50-60% of the pond surface. Submerged oxygenating species, one bunch or 7-10 stems, per square foot of pond surface area compete with algae for nutrients. Scavengers, snails or tadpoles, should be added one per square foot of pond surface area. Care should be taken when adding fish. Stock up to 1” of goldfish, fantails and shubunkins or 1/2″ of Koi, to 3-5 gallons of pond water. Avoid overfeeding.


Water movement and filtration are now standard for the water garden. Only rarely will a man-made pond achieve the desired appearance and balance envisioned by the owner without water movement and filtration of some kind. The unprecedented popularity of water gardening has driven the demand for more sophisticated and reliable filtration methods and equipment. The industry is deluged with hype but one thing remains true – biology is king. Good filtration systems support the biology of the pond, they don’t replace it. Water movement and filtration retard the proliferation of algae by removing the nutrient sources and eliminating anaerobic conditions that contribute to polluted and toxic conditions in the pond. Depending on filter and fish load, the total volume of water should be recirculated and filtered every 1-6 hours.

We Have extensively researched and tested pond filtration systems, pumps and skimmers from many manufacturers and features those products that are proven reliable and effective.Products from Aquarium Life Support Systems, Oase, Danner  Lifegard, and Atlantic consistently exceed expectations and are excellent choices for a variety of applications.

These Pond Solutions cover filter, UV Sterilizer and Pump selection:

4. Filtration
5. Pond Filters
6. UV Sterilizers and Green Water
7. Pumps – Sizing and Choosing


Like any other landscaped or bedded area, of the yard the pond requires maintenance. Good maintenance habits are essential to reduce algae problems in the garden pond. Fish waste and decaying plant material provide nutrients to algae populations and contribute to anaerobic conditions that deplete critical oxygen levels. Intake filters placed on the bottom of the pond collect debris and help eliminate sources of pollutants. Occasional vacuuming and partial water changes may be necessary to reduce contaminants and help keep the pond healthy and clear. Regularly scheduled water tests are essential to the healthy pond. Regular water testing can alert the pond keeper to impending problems long before symptoms become obvious.

Water Garden Cleaner

This is an excellent water conditioner that breaks down organic wastes that promote algae growth.


Sometimes, despite the bests efforts of the keeper, algae gains the upper hand and stronger methods are required to get it under control.


Straw and barley Straw Extract by Aquarium Life Support Systems, specific for string algae, and Water Garden Cleaner to combat floating algae, are good preventatives. This product also works as a fungicide and stimulates the growth of plants. Algae by Fritz is a reliable algicide that is safe for use with fish when the directions are followed. Colorants, like Black Lagoon and Blue, tint the water and provide shade against algae growth.

Algae is an unavoidable and recurring part of pond keeping. Getting and keeping it under control is a combination of good equipment and proper maintenance. Once a good balance of conditions is achieved, the garden pond will be a source of endless pleasure.

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