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Algae Bloom Treatments

When the level of nutrients --- particularly nitrogen or phosphorous --- in a body of water is too high, algae that thrive off these nutrients can multiply rapidly. The resulting blue-green, brown, or red clumps of algae that cover the surface of the water are called algae blooms. These blooms can be so dense that they lower levels of oxygen in the water, causing fish and other organisms to die; they may also release toxins into the water. Algae blooms can be controlled through chemical, biological, physical or mechanical means.

Chemical Treatments
- Copper sulfate and chelated copper compounds are algaecides that can be used to directly kill the algae. Chemical colorants and dyes are available that shade parts of the spectrum of sunlight that reach the algae, inhibiting its growth. However, these chemicals can be toxic to fish and other animals. When potable water is infested with algae, municipal authorities may treat the water temporarily with copper herbicides to decrease the algal count and make it more palatable to humans.
Biological Treatments
- Silver carp are effective at controlling blue-green algae and other floating types of algae, while grass carp eat submerged algae that attach to aquatic weeds. As biological control agents, carp are cost-effective; however, carp populations can expand out of control in areas where they are employed as biological treatments, or they may eat native vegetation in addition to or instead of the algae. Bacteria can also be added to the water to use up the excess nutrients off of which the algae feed.
Physical Treatments
- During aeration, the water is oxygenated and stirred, which can disrupt the blue-green algae and result in a shift to other, preferred algal species. Aeration reduces algal growth rather than killing or removing the algae; however, it protects the other organisms in the pond by helping the dead algae decompose naturally.
Mechanical Treatments
- In situations where dense mats of algae float to the surface, harvesting machines can be used to lift the mats out of the water. For smaller bodies of water, such as decorative ponds, electronic skimmers can remove the algae from the water's surface. This method has the benefit of removing the nutrients the algae have taken up along with the algae itself, which can temporarily interrupt the growth of the remaining algae.

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