Planktonic Algae
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Planktonic Algae (Chlamydomonas, Chlorella, Euglena, Closterium, Anacystis spp.)

Planktonic Algae

Planktonic algae are floating microscope plants that are normal and essential inhabitants of sunlit surface waters. There are literally millions of floating planktonic algae and these color pond water shades of green, blue-green, brown or variations in between. Planktonic algae that color the water is often called a "bloom" or "algae bloom". Many species of algae are involved in algae blooms and these species change over time based on temperature, light, nutrients, and other factors.

Planktonic algae blooms are considered desirable as the beginning of the pond food chain. In fact, fertilization programs are often used to promote algae blooms and thereby support a larger fish population. Planktonic algae is desirable for shading the pond bottom (in areas over 2 feet deep). This shading suppresses the establishment of rooted aquatic plants. However, to much planktonic algae can cause oxygen depletions and fish kills.

Planktonic algae are least abundant in winter when cold water temperatures inhibit their reproduction and growth. This is why most ponds are their clearest in winter. As ponds warm in April, reproduction by algae increases greatly and the spring algae “bloom” occurs. The pond’s water becomes distinctly less clear, with water color becoming greenish or brownish depending on the algae species present.

Planktonic algae will turn your pond murky. Planktonic is a term that covers all forms that are suspended in water. Under a microscope, you would see that these algae have threadlike "tails" (flagella) that allow them to move though the water.

Severe algae blooms can cause problems for fish. If the bloom dies-off suddenly, a fish summer kill can result due to oxygen depletion. Bloom die-off can be caused by weather changes, a sudden decrease in nutrient levels, or treatment of the pond with an herbicide.

Planktonic Algae Control Options


Floating, planktonic algae cannot be mechanically or physically controlled, except by replacing the pond water. Exchange of water from a well or other source that does not have an algae bloom will dilute the planktonic algae in the pond. This is not a practical option for most pond owners unless their ponds are very small and they have wells close by. Non-toxic dyes or colorants prevent or reduce aquatic plant growth by limiting sunlight penetration, similar to fertilization. However, dyes do not enhance the natural food chain and may suppress the natural food chain of the pond.


While many microscopic animals (zooplankton) eat planktonic algae there is no practical way to increase their populations, so no biological control is possible.


The active ingredients that have been successful in treating filamentous algae include copper based compounds (E), sodium carbonate peroxyhydrate (G) E = excellent, G = good.

Resources: Department of Wildlife and Fisheries Sciences, Texas A&M University

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Product to Control Planktonic Algae

Planktonic Algae

GreenClean is a Sodium Carbonate Peroxyhydrate based herbicide. These contact herbicides are used for control of blue-green algae. Hydrogen peroxide is the active agent in this algaecide. It is not effective on the macroalgaes, Chara or Nitella, or on any higher plants. GreenClean is the safest algaecide on the market for use around fish.


Redwing is a liquid diquat formulation that has been effective on coontail. It is a contact algaecide and herbicide. Contact herbicides act quickly and kill all plants cells that they contact.

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