How to Kill Algae in a Pond: 14 ways

How to kill algae in a pond discovering why they appear + 12 points on how to organize your own small lake +14 ways how to cope with algae + 4 effective pieces of advice.


Algae are said to become one of the elements of the future biofuel but meanwhile they are a real trouble for your small pond and fish.

If you properly approach the situation, you’ll be able to deal with the spread of the weed in a pond.

In today’s article, we are going to discuss how to kill algae in a pond.

The reasons why algae appear in a pond

Algae are never the problem with the water but simply the outer manifestation that something is wrong.

The nutritive substances are said to be the common dilemma of all basins.

The major reason why weed and other unwanted plants grow in the ponds is the high concentration of nutritive substances that allow them to do it.

The parts of grass, leaves, effluents from meadows, farms and pasture fields, animal by-products from ducks, geese, fish and other organic materials (such as dead plants) – these are only a few of the widespread supplies of nutritive (biogenic) substances in the ponds.

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All such sources supply the pool with much nitrogen and phosphorus.

These elements facilitate the plants to appear and spread.

The secret of how to stop the algae’s growth is to restrict the amount of nutritive (biogenic) substances in the small lake.

12 steps how to organize a pond so that algae did not grow in it

  1. Plan the location of a pond so that you used the benefits of shadow parts of your yard.

    However, you should never place it close to the tree because the leaves and turpentine are sure to fall and bring much harm.

  2. Build or change your small lake so that the liquids from the backyard were unable to get there.
  3. Pick an aerator with little bubbles and install it in the deepest zone of your small lake.

    Make it work 24/7 and it will develop the natural movement of water.

    In its turn, it is likely to make a favorable environment for fish and eliminate the harmful impact of weed.

  4. Some special plants might stop the sunlight from getting to the wide tracts of smooth water.

    A perfect option will be to have water hyacinth, lotuses, and lilies.

  5. Add the underwater weed.

    It consumes the nutritive substances which are significant for the algae.

  6. Buy the snails as they are likely to eat all weed.
  7. Breed the frog larva.

    They raven on algae and also they cope with the mosquitos and kill the insects’ eggs.

  8. Supply your fish with as much food as they are able to consume within 5 minutes.

    The rest of it is likely to rot and facilitate the weed’s growth.

  9. Regularly clean the filters.

    The wasted filters may disturb the spread of useful bacteria.

    Consequently, this will let the unnecessary plants bloom.

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  10. Apply the ultraviolet sterilizers as they break the walls of the algae and kill them this way.
  11. Use a skimmer or a net to clean the surface.
  12. Get rid of this trouble by the special vacuum cleaner.

9 ways how to kill algae in a pond

There exist many accessible ways to control and prevent the occurrence of algae.

Every method influences differently, in various conditions and with different efficiency.

Some methods work only within one cycle of algae’s bloom, while others can work within a longer period of time.

In the article below we are going to discuss how to kill algae and all pros and cons of these methods of cleaning:

  1. Paints.

    The technique of dying is rather old.

    Nevertheless, it is still used and it still works.

    The special liquid or powder paint of blue or black color is applied to make the water dark and reduce the penetration of sunlight which is required for the algae’s growth.

    This option of dealing with the situation won’t work in the ponds which are meant for irrigation or are connected to other lakes because the paint is washed away by the streams.

  2. Bacteria and enzymes.

    The application of useful bacteria is not a chemical way because the live organisms are mostly working and consuming the nutritive substances which would be otherwise accessible for the algae.

    Bacteria block the covering of the lower algae and their metabolism works only through the cells’ walls of their caulis.

  3. Ultraviolet sterilizers.

    The ultraviolet lamp is the essential part of the system for cleaning the water.

    Green water goes through the ultraviolet blocks where the algae’s surface is burnt by strong ultraviolet light.

  4. Dried barley grass.

    The research has shown that the dried barley grass helps to balance the quality and decrease the level of pH as well as the water hardness. It may also influence on the speed of growth of some unwanted plants.

    The barley grass under the influence of water and sunlight is decomposed and its by-product is peroxide.

    It prevents the development of both thread and blue-green algae.

    The average dose for the private basins is 25 kilos of dried barley grass for 1000 square meters of the lake surface in case it is relatively shallow – 1,2 – 1,5 meters deep.

  5. Skimmers.

    A skimmer is a tool which allows people prevent the appearance of algae.

    It gathers the rubbish on the surface before it gets down and starts to rot.

    A skimmer usually keeps the trash from the surface in the adjoining filters and then it is cleaned mechanically.

    Skimmers are not often used in big ponds or lakes.

    Nevertheless, they are perfect for small and decorative ones.

  6. The products which contain copper.

    The most widespread product based on copper is the granulated copper sulfate.

    The low price and high effectiveness on blue-green and thread algae explain why it is so widely used.

    Nevertheless, one must account that the copper is poisonous for certain species of fish (such as gudgeon and salmon fishes), snails and other cold-blooded.

  7. Fishes.

    Tilapias eat blue-green and thread algae in the ponds.

    However, it is a tropical fish which has stress when the temperature falls to 10 degrees.

  8. Products based on herbicides.

    Products based on herbicides are seldom applied on the natural lakes or agricultural lands.

    These things must be used precisely according to the recommendations of the manufacturers on how to kill algae instead of all plants in general.

    They have strict limits of use during fish breeding.

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  9. Physical removal of algae.

    The hand nets, rakes, and special vacuum cleaners are also required to remove algae.

    You can also eliminate algae from the stones by the scrapers and brushes.

5 additional ways how to kill alga in a pond

You can not completely kill all green thread algae.

However, you can take some measures to lower the possibility of their appearance.

Things, to which you should pay attention removing algae from the pond:

  1. Green thread algae do not like straight walls in the basin which go 40-50 cm deep.
  2. The upper facing plates of the sandstone must go behind the inner border of the pond for 15-20 cm and be higher than the water level of 5-10 cm.
  3. You must definitely put there as many swimming plants as possible.

    They are azole, big duckweed, water lettuce and hyacinth.

  4. Cleaner-fish and gray comets kill algae.
  5. You should use chemicals last of all because the overdose can kill all plants in your pond!

4 tips on how to kill algae in a pond

  1. In case the algae grow very fast and the fish starts to die, you should remove all water.

    Then, throw away all algae, clean the pool and pour new water.

    24 hours later you can let the fish back to the basin.

  2. You should definitely buy a pump, a filtration system and ultraviolet sterilizer of the suitable sizes.
  3. There are kinds of algae which are really useful for your pond.

    They secure the fish with food and conduct the manufacturing of nitrates.

  4. The liquids from the backyard must never get into your pond.

    Herbicides, pesticides, and other fertilizers can bring much harm to the condition of your small lake.

How to kill algae in a pond?

It’s rather hard to reach the natural balance in the unnatural pond.

However, you must know that any self-respected pond-maker who loves nature and tries to understand its laws is able to do it.

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