How To Clear Green Pond Water

How to clear green pond water?

This is a very good question because nothing is more annoying than having a dirty green pond.

Let’s get started.

1. How Does a Green Pond Form?

The reason a pond will go green is because of floating algae. But a pond only turns green when the growth conditions for the floating algae are good.

If the conditions are not good the beneficial bacteria will no longer be able to process the amount of waste. And the water will become polluted which will turn the water green.

This is because oxygen plants and floating algae battle for nutrients in pond water. And when oxygen plants lose the battle, they will not absorb all the nutrients from the water and the growth of the oxygen plants will decrease.

Which is something that floating algae love because they will thrive in nutrient-rich water. And before you know it the entire pond will be green because floating algae will grow very fast, especially in warm weather and high water temperatures.

Green water and poorly growing oxygen plants usually go together. And because floating algae is a small, single-celled plant it is impossible to remove every trace of it from the pond by hand or with a filter. Keeping balance is key.

Let’s go to step 2 of how to clear green pond water.

2. How to Ensure Good Water Quality With Optimal Water Values

The first important step will be testing the water hardness. Because rain, hail, and snow will gradually make the pond water softer. And a green pond is usually but not always the result of incorrect water values.

The water hardness indicates how many minerals are present in pond water. These minerals form nutritional salts for the oxygen plants.

Oxygen plants absorb these nutrients from the water which lowers the growing conditions for floating algae. And not only will this ensure that oxygen plants can grow better but also because optimal water values ​​make it easier to achieve a great biological balance in a pond.

A water pond test kit will help in figuring out what the water values are. Check for water hardness (GH) and carbonate hardness (KH). GH should be between 8°and 12° and KH should be between 95ppm and 150ppm (parts per million)

  • GH levels are fixable with Velda GH Plus. Read the instructions on the bottle on how to use it.
  • With KH levels I recommend Velda KH Plus. Read the instructions on the bottle on how to use it.

By keeping the water values in balance. Floating algae will not have a chance to grow insanely fast because plants will eat all the nutrients. If this step is neglected the underlying cause of the growth of floating algae will remain which will turn the water green quickly.

Clear Pond Water
Clear Pond Water

Let’s go to step 3 of how to clear green pond water.

3. How to Fight Green Algae for a Clear Pond

The second step will be removing floating algae with an algae fighter like Microbe-Lift/AlgAway 5.4 because this will help in stopping algae growth. But first, remove as many floating algae as you can before adding any kind of product, and always read the instructions on the bottle.

Microbe-Lift/AlgAway 5.4 will kill the floating algae and as a result, they will float on the pond kinda like flakes. Carefully remove the dead algae from the pond.

Because if the dead algae remain in the pond they will fall down to the bottom of the pond. This means the bottom requires cleaning as well. Definitely scoop the dead floating algae out of the pond to save time in the long run.

How To Clear Green Pond Water
A Pond Covered Partly in Floating Algae

Let’s go to step 4 of how to clear green pond water.

4. How to Ensure Proper Aeration to Fight off a Green Pond

The main reason floating algae grows out of proportion is because of an abundant food source and lack of water movement.

Leaves, fish waste, leftover fish food, natural organisms, branches, and other dirt will raise the levels of chlorine, carbon dioxide, methane, and other gases. And floating algae thrives on these gases.

With aeration, gases in the water will drop to normal levels and the biological food sources for algae decompose before they can eat. And without food, floating algae will not be able to repopulate.

Water movement is also very important for keeping algae away from feeding, nesting, and growing out of proportion.

An air pump, biological filter, or waterfall are great options to keep sure the water circulates.

Oxygen is not only important for life above water but also below water. Fish and plants need oxygen to thrive and it also keeps balance in a pond so make sure there is enough CO2.

How To Clear Green Pond Water - CO2
How To Clear Green Pond Water – CO2

Let’s go to step 5 of how to clear green pond water.

5. Oxygen Plants Will Help in Getting a Green Pond Clear

The last step should be done as of last because if you place new oxygen plants before the floating algae are gone there will not be enough CO2 in the water.

And plants will not be able to grow properly. Why it is better to wait with this last step until the water obviously turned more clear.

Water lilies are also affected by floating algae. Because of the turbid water, there will be less sunlight which will reduce the leaf formation underwater.

Oxygen plants absorb nutrients from the water as they grow. Which are otherwise used by floating algae. By adding enough oxygen plants the water will become less nutrient-rich and floating algae has less of a chance to grow.

Make sure that the pond is covered with oxygen plants for at least 50%. Great oxygen plants to consider and grow easily are, for example, waterweed, hornwort, and ranunculus.

Ranunculus Peltatus - Picture Credit Saxifraga - Rutger Barendse
Ranunculus Peltatus – Picture Credit Saxifraga – Rutger Barendse


Thank you for reading my article about how to clear green pond water.

A green pond is never fun but when floating algae is removed and the water crystal clear is. There will be nothing more relaxing then enjoying the beauty of a freshly cleaned pond.

If there are any more questions on how to clear green pond water, please leave them in the comment box below and I will do my best to answer them all.

Still new to the hobby of ponds and looking for more articles? Look no further and click here to gain more knowledge.

  1. What an informative post!  I had no idea that so much was going on in a pond! I have a couple of friends that have ponds and they are green. I will be sure to direct them to this page.  So much information.  What are some oxygen plants you would recommend for ponds for the UK climate?

    • Thank you for the kind words.

      For the UK Climate, I would recommend water crowfoot and/or water violet. Both are great oxygen plants for a pond. 

  2. Damn, that’s a good, informative article from what I remember about ponds! I won’t be building a pond anytime soon, but also works for a large aquarium too 🙂 Will definitely keep this in mind should I decide on a larger aquarium or even a pond in my back yard, except for a dog lol.


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