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Understanding Algae in Your Pond

Many property owners want backyard ponds because they enjoy the natural and relaxing feeling that water brings. They don’t want invasive pests interfering with their view, with the quality of their water or the health of the pond’s plant and animal life. Often, algae are viewed as antagonists, but they are not! Many people are surprise to learn that not all algae are “bad.” Here is what you need to know about the green stuff in your pond.

Algae’s Place in the Food Chain

A pond without any algae is not a healthy pond. This green “slime” serves as the base of the food web and thus a significant source of nourishment for fish, snails and many other creatures in a pond. Algae help oxygenate the water and remove nitrogen compounds, which can be harmful to fish at high concentrations. Algae are plants that convert sunlight and nutrients into food for the pond.

There is a wide range of algae species, but they are often thought of in two major groups:


Planktonic algae are suspended in the water and often give a green tint to the water. As the base of your food chain, they are indispensable in promoting healthy fish populations. There can also be too much of a good thing and at extreme densities of these algae can deplete oxygen and cause fish kills. Very high densities of planktonic algae can indicate excessive nutrient levels in ponds, something that requires proper management to reverse.


These algae reproduce and join simultaneously into long strings that form mats on the bottom of ponds. In midsummer, these mats will become buoyant, floating to the top in broad filaments or stringy mats. At moderate levels, filamentous algae contribute to the food web and therefor provide food for fish. If growth runs out of control, it can interfere with activities like swimming and fishing. Heavy “blooms,” can deplete oxygen in the pond and be dangerous for fish populations.

Algae’s Role in Your Pond

A healthy algae balance is crucial for pond health. Sometimes different pond management strategies require different tactics for algae: if you choose a trophy bass pond, you may benefit from an abundance of algae growth. If your pond is more of a backyard swimming pool, you may want to reduce algae growth. It comes down to recognizing what you need and managing your pond to achieve your desired goals.

Excessive algae growth is generally the result of excess nutrients in the pond. The first line of management is to control the entry of nutrients into the water. The next is to use aeration and beneficial pond bacteria to reduce nutrient loading already in the pond, but this process takes time. If immediate results are required, application of an appropriate algaecide may be the best course of action. 

If you aren’t sure of how to deal with your algae, give us a call and we will be happy to help you achieve the best result for your pond.