Preventing Algae Blooms from Taking Over Ponds and Lakes

Preventing Algae Blooms from Taking Over Ponds and Lakes

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Preventing Algae Blooms from Taking Over Ponds and Lakes

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Preventing Algae Blooms from Taking Over Ponds and Lakes

While driving around during the summer anywhere in the United States you will likely see some ponds and lakes covered with a green or blue substance. On close examination, what you will see are green mats of algae floating on the surface of the pond or lake.

What is algae?

Here are some facts about algae:

  • Algae is a term used for a large group of photosynthetic plants that can form colonies or mats on the surfaces of a body of water.  
  • Algae colonies or mats can fragment into small pieces and continue to grow and spread across a body of water. 
  • There are as many as one million algae species.
  • Good algae, which make up the majority of algae species and often referred to as green algae and diatoms, serve as a foundation food source for numerous aquatic organisms.
  • Bad algae, which are fewer and referred to as cyanobacteria, blue-green algae (BGA), or harmful algal blooms (HAB), do not serve as a food source for aquatic organisms. 

What major concerns are there with algae?

The most important concern is with the occurrence of algal blooms. 

  • Algae blooms are a characteristic of bad algae (BGA or HAB). BGA cells clump together to form surface scum which appears on top of the water like chopped grass blades, or as thin blue/green mats, or as green paint spilled. 
  • Algae blooms have become a major concern for many lake and pond owners with outbreaks reported to have increased by 18 percent between 2018 and 2019 alone.
  • Algae blooms typically occur in the summer months when there is a lot of light, long days, warm days, and stagnant conditions.

What are Some Major Factors that Cause Algae Blooms? 

What are Some Major Factors that Cause Algae Blooms?
  • Pollution 
    • BGA/HAB feed on a steady diet of phosphorus and nitrogen. When phosphorus and nitrogen fertilizers applied in excess, these nutrients can enter water bodies via chemical runoff or soil erosion.
    • Poor sewage management also introduces phosphorus and nitrogen into surface water systems.
  • Light Exposure and Water Movement
    • Like all other photosynthesizing organisms, algae require the right amount of light to thrive.
    • Unlike good algae which thrive best in clear waters that are shallow, BGA/HAB have the ability to move throughout the pond or lake and adapt to variable conditions.
  • Turbidity and Temperature
    • Turbidity is a measure of how clear or cloudy a body of water is and impacts light exposure and temperature of the water.
    • The more turbid the water, the warmer the water will be, allowing the algae to grow faster.
    • As algae blooms continue to grow, the water becomes increasingly turbid, which fosters an environment for algae blooms to thrive.
  • Climate change
    • Higher air temperatures have a corresponding effect on raising water temperatures.
    • Higher water temperatures combined with increased stormwater runoff packed with nutrients can result in conditions favorable for algal blooms.
    • With a changing climate, HABs can occur more often in freshwater bodies and may become more intense.

What are the Consequences of Harmful Algae Blooms in Ponds and Lakes?

  • HABs known to produce and release toxins that kill fish and other animals. 
  • Harmful Algae Blooms can hurt aquatic life by blocking out sunlight within water bodies and clogging fish gills.
  • HABs can create ‘dead-zones’, which are areas in water with little to no oxygen where aquatic life cannot survive.
  • Toxins produced by HABs can be harmful to humans and pose a threat to public health through diminishing water quality or through affecting individuals with respiratory conditions.
  • HABs can make water unsafe to drink. Furthermore, when water is tainted with HABs, it becomes much more expensive and challenging to treat before it is safe to consume. Even after it is deemed safe to consume, the water may have an off-putting smell or aftertaste.

How can you Prevent Algae Blooms from Taking Over your Pond or Lake?

Now that you know (i) the difference between good and bad algae, (ii) how harmful algal blooms can have devastating effects on aquatic life, and (iii) how toxins released in water by HABs can harm animals and humans, let us look at how to prevent, manage, or control algae.

There are three methods used to manage algae:

  1. Chemical – which involves the application of algaecides. For example:
    • Copper salts and water soluble copper based algaecides.
      1. Copper sulfate, an old standby, disrupts the cell membranes in algae, which is inexpensive. It is less effective in hard water (which has high calcium and magnesium content), is toxic to fish at low pH, and most effective when water temperatures are above 60 F.
      2. Water soluble copper based algaecides disrupt cell membranes in algae and are relatively expensive. These algaecides can prevent copper from precipitating out of solution in hard water, and are most effective when water temperatures are above 60 F. 
    • Oxidants and hydrogen peroxide can be as effective on algae as copper but are much less effective on algae species that are more difficult to control.  These algaecides likely disrupt cell membranes and walls, work best where water pH range is 6.8 to 7.8, and at all temperatures. 
    • Dye materials are algaecides that are more expensive than copper sulfate but less than chelated copper. These algaecides work by blocking portions of the light spectrum necessary for photosynthesis. They should be used early in the season before algae has extensive growth. Also, it may not work well in waters that are less than 2 to 3 feet deep.
  2. Physical or mechanical – which involves raking or dredging, mowing, and harvesting the algae.
    • On a small scale this method can be highly effective. However, for large ponds or lakes, physical removal of algae blooms requires expensive harvesting equipment.
    • When algae is removed physically, the material needs to be taken out of the water and disposed of where the nutrients and fragments cannot re-enter the pond or lake. 
    • Repeat physical removal may be necessary during the growing season.
  3. Biological – which involves introducing plants or animals that compete with or feed on the algae.
    • Some type of carp fish will feed on mat forming algae when their food source is depleted.
    • The use of carp to control algae is variable and will limit the potential to use copper-based algaecides.

Enhancing control of algae blooms with adjuvant


Camberato, D.M. and R.G. Lopez. 2010. Controlling Algae in Irrigation Ponds. Purdue University Extension Service publication HO-247-W. [Verified July 1, 2021]

Environmental Resilience Institute, Indiana University. 2021. Climate Implications – Harmful Algal Blooms. [Verified July 1, 2021].

Environmental Working Group. 2019. Algae Outbreaks Up by Nearly One-Fifth in 2019. [Verified July 1, 2021].

Guiry, M.D. 2012. How many species of algae are there? Journal of Phycology 48: 1057-1063. DOI: DOI: 10.1111/j.1529-8817.2012.01222.x.,  [Verified July 1, 2021].

National Institute of Environmental Health Sciences. 2021. Algal Blooms. [Verified July 1, 2021]

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