Spirogyra, Anabaena, Oscillatoria, Lyngbya, Pithophora spp., etc.
For information on Controlling Algae in Farm Ponds, see our video and publication below:
Managing and Controlling Algae in Ponds Manual
Non-Herbicide Management Options
1. Physical Management Options
Filamentous algae can be raked or seined from the pond.
Fertilization to produce a phytoplankton or algal “bloom” can prevent the establishment of filamentous algae if started early enough in the spring. Fertilization also produces a strong food chain to the pond fish.
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:
Many types of mechanical removal devices are available that cut or chop up aquatic weeds. It is important to remember that many submerged plants regrow from fragments, so removal of cut fragments may be necessary to keep from spreading the unwanted plant.
Companies that make cutters and rakes include but are not limited to:
2. Biological Management Options
Tilapia will consume filamentous algae but are a warm water species that cannot survive in temperatures below 55 F. Therefore, tilapia usually cannot be stocked before mid-April or May and will die in November or December. Recommended stocking rates are 15 to 20 pounds of mixed sex adult Mozambique Tilapia (Oreochromis mossambicus) per surface area. Tilapia are often not effective for vegetation control if the pond has a large bass population due to intense predation. In Texas, stocking tilapia requires approval from the Texas Parks and Wildlife Department if the pond is in the designated “conservation zone” to ensure tilapia cannot escape and negatively impact imperiled native fishes. Tilapia must be purchased from a permitted seller regardless of zone. In other states, check with your County Extension Agent for the legality of stocking tilapia.
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 Filamentous Algae include:
- Copper Sulfate (Rated: Excellent)
- Copper Chelated Complexes (Rated: Excellent)
- Diquat (Rated: Good)
- Alkylamine Salts of Endothall (Rated: Good)
- Flumioxazin (Rated: Good)
- Sodium Carbonate Peroxyhydrate (Rated: Good)
These rating are based upon the U.S. Army Corps of Engineers aquatic herbicide trials.
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) Diquat
Diquat is a contact algaecide and herbicide. Contact herbicides act quickly and kill all plant cells they come in contact with.
Common trade or product names include but are not limited to:
4) Alkylamine Salts of Endothall
Alkylamine salts of endothall come in both liquid and granular forms. It is a contact herbicide.
Common trade and product names include but are not limited to:
Hydrothol can be toxic to fish.
5) Flumioxazin
Flumioxazin is a water dispensable granule that is to be sprayed or injected after mixing. It is a broad spectrum, contact herbicide. Contact herbicides act quickly. Flumioxazin should be applied to actively growing plants and a surfactant (a substance that reduces water tension) will be needed if the herbicide is applied to foliage of floating or emergent plants. Water pH needs to be below 8.5 or flumioxazin will rapidly degrade and lose effectiveness.
Common trade and product names include but are not limited to:
6) Sodium Carbonate Peroxyhydrate
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:
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).
To see the labels for these products click on the name. Always read and follow all label directions. Check label for specific water use restrictions.
Cultivation Options
Filamentous algae are seldom encouraged. It could be encouraged by transplanting mats of filamentous algae from another pond and not fertilizing to encourage a planktonic algae bloom.
Questions?
If you need assistance, contact the Ag & Natural Resources agent in your county or hire a professional.