A Diagnostics Tool for Pond Plants and Algae

How to Control Golden Algae

Non-Native

Golden algae covering water

Prymnesium parvum

More Info & Photos of Golden Algae

Non-Herbicide Management Options

1. Physical Management Options

Golden algae (Prymnesium parvum) cannot be mechanically or physically controlled, except by replacing the pond water. Exchange of water from a well or other source that does not contain the algae bloom will dilute the golden 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. Downstream release of golden alga may cause the death of fish, and liability could be an issue.

Golden algae prefer brackish or slightly saline waters. If pond water can be maintained fresh either through the addition of well or surface water then golden algae growth may be suppressed or eliminated.

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 will suppress the natural food chain of the pond.

Some examples of non-toxic dyes and other products include but are not limited to:

2. Biological Management Options

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

Herbicide Control Options

Always read the product label for directions and precautions, as the label is the law. Click on the name of the product to see the label. Read the label for specific water use restrictions.

The active ingredients that have been successful in treating Golden Algae include:

  • Copper Sulfate (Rated: Excellent)
  • Copper Chelated Complexes (Rated: Excellent)
  • Sodium Carbonate Peroxyhydrate (Rated: Good)
  • Potassium Permanganate (Rated: Excellent)
  • Ammonium Sulfate (Rated: Good)

These ratings are based upon the U.S. Army Corps of Engineers aquatic herbicide trials.

The key to controlling a Golden Algae bloom is to treat the algae before it becomes toxic or before it releases toxins. To do this the pond water has to be examined for the presence and density of golden algae. This examination takes a good microscope, a hemocytometer and knowledge of the organism. This service is currently being provided by:

The chemical treatments described below do not detoxify the golden alga toxin, with the exception of potassium permanganate. The algaecides below kill the P. parvum, but the water will remain toxic until fresh water dilutes it out or it is broken down by natural processes over time (usually within a few weeks).

1) Copper Sulfate

Copper Sulfate or “blue stone” is probably the most commonly used algal treatments because of its availability and low cost. Copper sulfate comes in several forms depending on how finely it is ground. Smaller crystals will dissolve easier than larger crystals. In very hard water it is difficult to use copper sulfate because it binds with the calcium, precipitates out of solution, and renders the copper ineffective as an algaecide.

All copper compounds can be toxic to fish if used above labeled rates and can be toxic in soft or acidic waters even at label rates. Before using copper it is best to test the pond water’s alkalinity and adjust copper treatments to alkalinity concentrations. For additional information on using copper sulfate see the SRAC #410 Calculating Treatments for Ponds and Tanks.

Common trade or product names include but are not limited to:

2) Copper Complexes

All copper compounds can be toxic to fish if used above labeled rates and can be toxic in soft or acidic waters even at label rates. Before using copper it is best to test the pond water’s alkalinity and adjust copper treatments to alkalinity concentrations. For additional information on using copper sulfate see the SRAC #410 Calculating Treatments for Ponds and Tanks.

Common trade or product names include but are not limited to:

3) Sodium Carbonate Peroxyhydrate (SCP):

These are contact herbicides for control of some algae and have been shown to kill golden algae. Hydrogen peroxide is the active agent in this algaecide. SCP is not effective on the macroalgaes, Chara or Nitella, or on any higher plants. The toxin of golden algae is not detoxified by this algaecide.

Common trade or product names include:

4) Potassium Permanganate:

Potassium permangante is not a registered algaecide, but an oxidizing agent. If used, it will kill algae and neutralize the toxin. Potassium permanganate is usually used at 2 mg/L, but a higher concentration may be required if the pond water has a high oxidative demand. High concentrations (in excess of 2 mg/L above the oxidative demand) may be harmful to fish and other aquatic organisms.

5) Ammonium Sulfate:

Ammonium sulfate is not a registered algaecide, but a type of fertilizer. The ammonium ion of this compound is what kills the golden algae. The ammonium ion is also toxic to fish and many other aquatic organisms. Therefore, great care must be taken to apply this compound at the appropriate concentration. The appropriate concentration has to be calculated of each particular pond and per conditions of the pond immediate before application. Water quality tests for pH, temperature, and ammonia are necessary to calculate the concentration of ammonium sulfate to use.

For more information on golden algae and the use of potassium permanganate and ammonium sulfate to control it, see the TX Parks and Wildlife publication at: http://tpwd.texas.gov/landwater/water/environconcerns/hab/ga/research/

Precautions

One danger with any chemical control method is the chance of an oxygen depletion after the treatment caused by the decomposition of the dead plant material. Oxygen depletion can kill fish in the pond. If the pond is heavily infested with weeds it may be possible (depending on the herbicide chosen) to treat the pond in sections and let each section decompose for about two weeks before treating another section. Aeration, particularly at night, for several days after treatment may help control the oxygen depletion.

One common problem in using aquatic herbicides is determining area and/or volume of the pond or area to be treated. To assist you with these determinations see SRAC #103 Calculating Area and Volume of Ponds and Tanks.

Many aquatically registered herbicides have water use restrictions (See General Water Use Restrictions).

Cultivation Options

This plant is not native to North America and should not be introduced into new water bodies and should be treated with herbicide when present.

Questions?

If you need assistance, contact the Ag & Natural Resources agent in your county or hire a professional.