How to Get Rid of Pond Algae: Step by Step

Pond Algae

Pond algae are not only unattractive, but they can also be harmful to your fish and plants. Algae growth in ponds can create an oxygen-deficient environment that will suffocate your fish. If you are tired of scrubbing the green slime off the sides of your pond or getting slimed when you go fishing, then this post is for you! We will discuss how to get rid of pond algae step by step so that you can enjoy a clear, healthy pond again!

What helps against algae in the pond?

A garden pond is a sensitive ecosystem that can easily become unbalanced. A common problem is algae, which spread rapidly under suitable conditions and take over the habitat of other pond inhabitants such as fish. Nutrient-consuming aquatic plants and small animals, such as snails, help to combat algae. Generally reduce the direct sunlight on the water and the pH value, if necessary. In addition, pond water must be kept in constant motion by means of a pump. If filamentous algae form, remove them by hand. If the removal of algae should be quick, use an environmentally friendly algae remover.

The most radical measure of algae control is a complete water change including cleaning of the pond. If there is no possibility to do this, a pond inoculation can help. This involves adding a few liters of water from a healthy pond. The microorganisms in the “healthy” pond water ideally destroy the algae in the diseased pond. Also, during prolonged dry weather, balance evaporated water with freshwater to maintain the balance of nutrients in the pond.

How do algae develop in the garden pond?

Often overfertilization is the cause of an algae bloom, for example, due to fish food, large amounts of fish excrement, or too dense plant stocking. Contamination by leaves and other dead plant parts can also increase the phosphate level in the water and thus promote algae growth. Strong sunlight and too little oxygen also promote algae growth.

Use special pond soil when building or redesigning the pond. Plant and potting soil contains too many nutrients and provides an ideal breeding ground for algae.

Important: Over the course of the year, the oxygen and nutrient content of a pond is subject to natural fluctuations that return to normal by themselves. However, if the balance in the pond threatens to “tip over”, act quickly.

How to remove algae in a pond in 6 steps

1. Perform pH test

At a glance

  • Determine pH value with the test kit.

This is how it works

Determine the pH value via a test kit for pH regulation. Regular pH measurement helps to keep an eye on the water quality and the nutrient content of the pond. The pH value is ideally between 6.8 and 8.2. High content of nutrients such as phosphate in the water increases the pH value. If the pH value is too high, this, in turn, promotes algae growth.

2. Lower pH value

At a glance

  • Use bark mulch in the pond
  • Use pH-minus preparation
  • Add groundwater or exchange water

This is how it works

Low humic acid substrates such as peat or bark mulch help lower the pH of the pond water. Use a net when adding substrates to remove them from the pond water. Alternatives include a controlled supply of groundwater from a cistern or the addition of environmentally safe pH minus


Exchanging about 10% to 20% of the water volume over a period of two days can also lower the pH. If you pipe rainwater from a rain barrel into the pond for this purpose, filter the water beforehand. Filtering prevents the excessive entry of dirt particles and nutrients. Rainwater collected from gutters is often rich in nutrients.

3. Ensure oxygen supply

At a glance

  • Avoid oxygen deficiency in the pond
  • Using pond pumps and filters

This is how it works

Filter systems that regularly clean and oxygenate the water are especially important in ponds stocked with fish. But they are also recommended for pure plant ponds of small size – among other things, to contain the spread of algae.

Avoid oxygen deficiency in the garden pond and use pond pumps and filters. Also, eliminate floating algae with the help of a UVC pond clarifier. Often already integrated into filter systems, the UVC clarifier combats suspended algae and germs using a UVC lamp that produces ultraviolet light.

A supplement or alternative to the pond pump is an environmentally friendly oxidizer, with which you also enrich the water with oxygen. The capacity of filter systems, pumps, and oxidizers depends on the pond volume and you calculate this as follows: Pond volume = (width x height x depth)/2

4. Use aquatic plants

At a glance

  • Correctly assort pond plants
  • Choose the right amount of water plants
  • Remove excess plants

This is how it works

The right composition of pond plants ensures a balanced ecosystem and minimizes algae growth. The quantity of aquatic plants is also critical. An overabundance can lower oxygen levels in the water and increase nutrients. Both of these factors promote algae blooms.

Therefore, if you have an acute problem with floating algae, check the quantity and composition of your pond plants. Remove excess plants and use nutrient-consuming water plants such as water lilies, hornwort, or water feathers to reduce the nutrient supply in the pond.

Note: Remove leaves, dead plants, and filamentous algae from your garden pond, for example, with a flat landing net or lake rakes. A skimmer will help you with regular cleaning.

5. Suck off algae

At a glance

  • Use a pond vacuum cleaner
  • Remove floating thread algae

This is how it works

Use a sludge and pond vacuum cleaner to clean your pond. For example, you can use the vacuum to effortlessly remove filamentous algae floating freely in the water. Even algae that adhere firmly to stones or the bottom can be removed with the pond vacuum cleaner. Use specialized attachments to remove algae from large areas as well as the smallest crevices.  Algae from large areas as well as the smallest crevices.

Note: Watch out for small animals such as fish or snails and proceed carefully when cleaning the garden pond.

6. Use algae blocker

At a glance

  • Reduce growth conditions for algae
  • Increase solar reflection of the water

This is how it works

In the case of an acute algae bloom, the use of algae blockers can help. These agents usually combat algae by reducing necessary growth conditions. For example, the algae blocker can reduce an excess of phosphate in the water to deprive algae of an important source of nutrients. Another variation of algae control is the introduction of natural tannic and humic acids, which increase the solar reflectance of the pond water, thus depriving algae of necessary sunlight exposure.

Only resort to chemical aids in emergencies and make sure the dosage is correct according to the manufacturer’s instructions as well as the environmental compatibility of the algae blocker. The best solution for the permanent prevention of floating algae and for healthy pond water is a biologically working filter system including a UVC filter.

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