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Why Do Ponds Go Green In The Spring?

28th October

As a pond-owner, spring means only one thing. Green pond water. So why does this happen? In this blog, we will cover what causes green pond water in spring and how to treat it.
Not only is green water unattractive to look at, but it is also a telltale sign that your pond parameters may be off.

What causes green pond water?

Ponds turn green due to the growth of microscopic algae, or blue-green algae. Algae thrives in warm, nutrient-rich water that has access to an abundance of sunlight. In these conditions, algae can quickly reproduce, also known as an algae bloom. Although it is called green water, the growth of microscopic algae could change the colour of pond water to not only green but even shades of blue or brown.

Algae blooms can be caused by a number of factors. The first factor is nutrient-rich water. Nutrient-rich water can include high levels of nitrogen and phosphorus which can come from organic debris such as twigs, leaves or fish food. Another important factor that can lead to an algae bloom is warmer weather and long days, making spring the perfect time for algae bloom to occur.

Algae blooms can be harmless however, if left untouched could become dangerous to fish and even humans.

How to treat green water naturally

There are multiple ways to treat green water naturally.

Increase aeration: A fountain or air stone is a great way to increase oxygen levels in your pond. Increased oxygen levels encourage the growth of beneficial bacteria which reduces the amount of algae in water.

Pond plants: Pond plants is another way to increase oxygen levels in your pond, whilst also reducing the amount of sunlight that reaches the water. Discover a complete guide to pond plants here.

Barley straw: There is a chemical in barley straw that inhibits the growth of algae. Simply scatter it over the top of the pond. This method can be unreliable.

Pump and filter: A pump and filter can help maintain water quality by filtering out excess nutrients. The beneficial bacteria in the system will break down the organic matter.

Beneficial bacterial treatment: An effective way to remove green water is with a beneficial bacteria treatment such as Envii Winter Pond treatment. Envii Winter Pond Treatment works to temperatures as low as 4°C which makes it perfect for treating green pond water in Spring during the last frosts. Its task-specified bacteria digest the organic debris that will have accumulated over the autumn, winter months. Continue to treat your pond with Envii Pond Klear to maintain clear pond water year-round.

Tried these methods and your pond still isn’t clear? Discover 11 reasons why your pond isn’t clearing.

Related Products

  • Front view of Envii Winter Pond Treatment

    Envii Winter Pond Treatment

    Clears green water and reduces sludge in ponds over winter.
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  • Front view of Envii Pond Klear - Pond water treatment from Envii

    Envii Pond Klear

    Clears green pond water and prevents algae.
    Add to Basket

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About the author


Chief Executive Officer

If eating was an Olympic sport, Olly would hold the gold medal. He once fit 15 giant marshmallows in his mouth, consumes exactly 4,000 calories a day and even admits that 90% of his dreams involve food. At Envii, he specialises in all things e-commerce, spending time devising ways to improve sustainability and delivering exceptional service. All whilst eating, of course.

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