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Blue-Green Algae (Cyanobacteria)

Blue-green algae is not an algae, but a bacteria called "cyanobacteria." This bacteria can produce produce toxins that can cause liver damage, gastroenteritis, and, at times, death if ingested by livestock.

Identifying blue-green bacteria

Blue-green algae typically has a shimmering, blue-green colour. It may also have a foamy sheen-like appearance that looks like spilled paint floating on top of the water. Heavy blooms appear like a solid shimmering blue-green sheen across the water's surface, or have an appearance and consistency similar to pea soup. The blooms are dispersed within the water an unattached to solid objects unlike filamentous algae.


Warm daytime conditions during the months of June, July, August and September, combined with a stagnant, nutrient-rich body of water like a dugout, accelerate the growth of algae, including blue-green algae.

Blue-green algae
Photo courtesy of: Dr. Ron Zurawell, Ph.D., P.Biol.
Limnologist/Water Quality Specialist,
Alberta Environment

Time of year

Blooms of cyanobacteria begin to appear during the month of June, and persist throughout the warm summer months.


The most common treatment of blue-green algae in an open dugout or pond is with a registered product containing copper sulphate. Always read and follow label instructions for proper treatment

Whether the blue-green algae dies on its own or by treatment, when it dies it will release its toxins into the water. Therefore, it is recommended that 12 to 14 days should pass prior to any livestock, pet and/or human contact with the contaminated water to allow the toxins dissipate. If treating a dugout containing fish, it is recommended that only one-third of the dugout should be treated, using one-third, by weight, of the recommended copper sulphate product, applied in treatments over a three-day period.

Do not use more than the recommended amount of the registered copper sulphate product. Higher levels will destroy some of the beneficial organisms such as zooplankton, that actively feed on bacteria and algae.

Table 1. Approximate Dugout Capacities (Water depth 14 ft., 1.5:1 side slope, 4:1 end slope)

Dugout Width      
Dugout Length 60 ft. 80 ft 100 ft
160 ft. 400,000 600,000 750,000
200 ft. 525,000 775,000 1,000,000
240 ft. 650,000 985,000 1,300,000
280 ft. 800,000 1,100,000 1,600,000

The treatment process described above applies to non-draining waterbodies, such as dugouts, which are wholly contained on private land. In the case of waterbodies that drain to adjacent properties or waterways, a permit for the chemical control of aquatic nuisances is required from Saskatchewan Environment.

Strong winds or disruption to the waterbody can also cause blue-green algae to die and release toxins. Monitoring your water sources is important.


Blue-green bacteria prefers freshwater dugout and pond environments that are high in nutrients such as nitrogen and phosphorus, and where there is little to no water movement. Moving water by means of natural flow or aeration disrupts water temperature gradients, and maintains a more even water temperature at all depths of the body of water. Aeration also ensures a healthy aerobic environment which will promote the constant cycling of nutrients, and prevent a build-up of nutrients from occurring. Utilizing healthy riparian areas as buffer zones and excluding direct livestock access to the water source will also reduce nutrient load of the water source.

Blue-green algae
Photo courtesy of: Dr. Ron Zurawell, Ph.D., P.Biol.
Limnologist/Water Quality Specialist,
Alberta Environment

Treatment Products

Most products use copper sulphate as their active ingredient. It functions as an algaecide and fungicide, and as such is registered under the federal Pest Control Products Act. For a list of registered products containing copper sulphate visit the Pest Management Regulatory Agency website.

Other products

There are a variety of registered products along with aluminum sulphate and hydrated lime that are coagulation products that bind to all bacteria. Once bound, the bacteria clumps together and sinks to the bottom of the dugout. While these products work to remove blue-green bacteria from the water surface, the dead blue-green bacteria cells can rupture, releasing toxins into the water over longer periods of time, as compared to treatment with copper sulphate products. Blue dyes are also commercially available to aid in preventing sun exposure to the water body, reducing the temperature and photosynthesis required for algae to grow.


It is important to monitor livestock water sources and to properly diagnose the algae bloom prior to treating to ensure accurate treatment. In the case of blue-green algae, err on the side of caution and remove livestock from the source to allow toxins to dissipate. Implement preventative measures such as off-site watering systems that prevent direct livestock access to the water source and aeration to keep the water cool and moving.

Contact your local Livestock and Feed Extension Specialist for more information on livestock water quality.

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