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How to Control String Algae Growth in Koi Fish Ponds

How To Control String Algae Growth In Koi Fish Ponds

String algae are basically green strands of algae which looks like strands of green hair. Generally, it is during the Summer season or when there is too much direct sunlight falling on to the pond the string algae can grow out of control. 

The String algae growth and rate of growth depends on many many factors and due to the complex relationship between the different nutrients dissolved in water.

These varying combination of nutrients types, minerals, sunlight its intensity and duration, Oxygen levels in water, water temperatures, changing weather conditions etc..etc. contribute to the growth of the string algae.

In any case, the quality of source water used to make up for water loss shall always be tested.

Uncontrolled growth of the string algae depletes the oxygen content in water which can lead to Koi fish fatalities. Some of the important tips which can be implemented to control string algae growth are detailed below.

These steps or procedures will help you to overcome the string algae problem without the use of algaecide/ in an eco-friendly way.

The very first thing to do is to measure the exact quantity of water in the water body or your garden pond. And also remember to test your pond water for all the important parameters and make sure all of them are in normal range, which includes the pH.

High pH and Phosphorus are potential causes of the string algae growth. If you have high pH or Phosphorus use Phosphorus Remover pack in the filter and use the pH lower additives to adjust the pH levels.

Calculate the fish load and feeding times so that we know how much waste is generated by the fishes. Please make sure that the fishes are not overfed. Since the unconsumed food will promote the growth of string Algae.

If there is a string algae problem avoid giving Koi fish food pellets with high Phosphate content.

The functions of the Biofilter system shall be checked and verified. If a UV system is incorporated in your filter system check the status of its bulb.

Do a 10% to 25% water change which will help greatly in bringing the nutrient levels back to normal.

Another important and inexpensive thing which we can do is to provide shades for the pond which can reduce the amount of sunlight falling into the pond. Trees which sheds fewer leaves is also a good solution.

Planting surface plants like Lotus and water Lilly will help positively in controlling the algae growth.

Physical removal of string algae if possible, remove as much of the string algae as possible using a long-handled brush. It will help the fishes to swim freely.

Most of these algae blooms occur due to excessive nutrient content in the water. String algae strive on these excess nutrients, to control this undesirable situation you may add beneficiary bacteria as per the ponds water capacity and Bioload.

Additional aeration systems shall be provided to ensure good O2 levels in water. so that the beneficiary bacteria can aerobically digest the plant and fish wastes quickly and completely.

This will clear the muck at the bottom of the pond which is one of the sources of nutrients for String Algae.

In a pond with High levels of oxygen and with good circulation of water the fish will grow faster and consume the right amount of food and there will no food leftovers.

You may also introduce adequate nos of grass carps / Rohu/ Catla etc can help clear up the string algae by eating them.

If these above method doesn't solve your problem in 30 to 60 days you may have to go in for a treatment using algaecide which can be expensive and at times cause stress for the Koi fishes.

Please always avoid using algaecide containing copper additives which are very harmful to the fishes as well as for the ecology of the pond.

For any clarification and for pond maintenance / algae solution kindly contact us via email or call +91-9400726668 we will be happy to guide you through.


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Kochi – 682005

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