Algaecide Overdosing in a Pond

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I have a pond of 3.5 m2 with Koi fish and a problem with algae so I would like to calculate the correct algecide dose for my pond.

How is the amount of algaecides calculated for a lake or a pond? Is there a formula?

Which factors, in addition to the amount of nutrients and lake size, affect the formula most?

What are the consequences of overdosing a pond or a lake with algaecide and what will happen to aquatic life? For how long will the effects of overdosing be noticeable?

What can be done to reduce the negative effects of overdosing a smaller pond with fish?

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11 Answers

  2. The normal algaecides to eradicate algae from ponds is copper sulphate & chlorine. Both have very high toxicity for fish and is not advisable to use. Alternatively I recommend the use of Chlorine Dioxide as it works by oxidation and toxicity studies have shown that it is gentler on the fish. 

    To start with, I recommend a dose of 1 ppm. Since the area of the Pond is 3.5 sq. mtrs. you need to know the depth of the pond as well. If the depth of the Pond is 5 mtrs then you have 22 cubic meters of water or 22,000 liters of water. A 1 ppm dose of 31% conc. product will require 70 ml of chlorine dioxide + 70 ml of Activator (15% Conc. Hydrochloric Acid). This should be added at night time so that the chlorine dioxide gets a chance to work through out the night. 

    In the morning all the algae would have settled to the bottom of the pond. You can use a net to remove the algae from the bottom of the pond. 

    As chlorine dioxide is biodegradable in the presence of sunlight, it breaks down into salt and water. It is for this reason that the chlorine dioxide treatment should be carried out at night time. 

    Once the algae is removed from the pond a maintenance dose of 0.2-0.5 ppm should be added every night. As nutrients will always enter the water and the algal blooms will occour from time to time. 

  4. Peter, I would stay away from algaecides for your pond. they are not good for fish. Instead use wind driven aerators. This will keep the oxygen level higher and help to prevent algae.

    1 Comment

    1. I agree with Tim. The algae will just adapt to the algaecide, hence the dosing is not as straightforward as you might think. It is best to consider aeration. The most efficient method of aeration is fine and ultrafine bubble generation, please email me at andrew@waterandoilsolutions.com.au if you would like to know more. I have experience in managing algae through this method in Australia.

  5. First you need to kow what species of algal blooms you are dealing with. Have the algae tested for species and then ask for dosing recommendations. You could use sonication a non-chemical approach or aeration as environmentally sound alternatives but they are species specific.

  6. An algaecide or algicide is a biocide used for killing and preventing the growth of algae.

     

    1    Natural algicides

    2    Synthetic algicides

    3    References

    4    External links

     

    Barley straw, is placed in mesh bags and floated in fish ponds or water gardens to help reduce algal growth without harming pond plants and animals

    Copper-based algaecides use copper to treat algae growth, and are most effective against mustard and green types of algae.

    Normally algaecide, like pesticide, is only a preventive and should be used throughout the pool season. But there are some algaecides that contain b14 or metals, such as copper or silver, which can kill algae. These algaecides may have to be added in large doses depending on the brand, but mixed with shock, can do the trick just as effectively as just plain shock.

     

    Phosphates are food for algae, phosphates are in the runoff water from landscaped areas, some are by-products from what you add to your pool.  This is food for algae and should be monitored quarterly and reduced or eliminated on a regular basis.  The laundry soap you use for washing clothes and bathing suits contains trace amounts of phosphates, it all adds up to promote algae blooms.  Test and eliminate on a regular basis.

     

    The use of UltraViolet or Ozone will help prevent the growth of algae from the spores it produces.  UltraViolet destroys the DNA and RNA chains of the algae and it dies unable to reproduce, Ozone will oxidize the spores and kill them on contact.  I prefer UV over Ozone because it is much easier to maintain in the long run. 

     

     

     

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  7. I would steer clear of algicides. Some of them are based on chelated copper which will persist in the pond for a long time. The dead algae would also have to be scooped out. Consider using a microbial solution since the problem is due to excess nutrients due to excreta from the fish and waste food. The natural bacteria will grow faster than the algae thus starving them of nutrients.

  8. Dear Mr Harris, 3.5 m² seem to be very small. Is it correct ? For big ponds exist chemical free, environmental sustainable solutions. Will be hapy to transmit a link. Contact us at dr.peters.consulting@t-online.de.

  10. I don't know what you consider a problem with algae, but i would caution you that if the algae is not removed from the pond, either before or after applying an algicide, the decaying algae will deplete oxygen in the pond, so aeration would be beneficial. Also, if the pond has little freshwater input, the waste from the fish could be causing your problem. Microbes in the pond will convert ammonia waste to nitrate, but evaporation from the pond will concentrate the wastes. Like with an aquarium, adding freshwater or better yet, exchanging a volume of the pond with fresh will prevent the nitrates from causing an algae bloom in the pond. If you can prevent the algae, you won't need algicide.

  11. Read the  label directions for the algicide that you are using. I don't know where you are; in the USA the label contains all of the requirements requiring dosing, including sensitivities. Each algicide is different. Use the least toxic to your fish.

    1 Comment

    1. I agree with Fred Heerbrandt, on the other hand; is the algae produced in your pond from the harmful types (Cyanophyta). So, be careful it may be toxins producing especially if the algicide cause decaying and the dose of algicide depends on the algae load or content.