Algae pond


Algae in the pond can be a real pest to your pond, from stubborn floating algae to troublesome filamentous algae. Algae is often caused by a lack of oxygen plants in the pond. We tell you all about the types of algae and how to control and, even better, prevent algae. Because too much algae can be detrimental to the health of your pond.

Simon van der Velde

Before you use chemicals to clean your opaque pond, consider oxygen plants. These plants not only purify the water, but also create a natural balance that fights algae. This is how you restore clarity to a green pond naturally.

Simon van der VeldePond specialist and aquatic plant breeder

Bacta Clear for a clear pond

Thread algae control and prevention

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Controlling and preventing floating algae

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Fighting thread algae in your pond

What are algae and how do they form?

Algae are unicellular or multicellular organisms that play a crucial role in aquatic ecosystems, including ponds. They are the primary food source for many aquatic animals and produce oxygen through photosynthesis. However, algae can also cause problems when they are abundant. Excessive algae growth leads to cloudy water, can be toxic and can smother other aquatic organisms. Several factors contribute to excessive algae growth, including excess nutrients (nitrates and phosphates), high pH, too much sunlight and lack of water circulation.

How do I prevent and control algae in the pond?

To prevent and control algae in your pond, a balanced approach is essential. Start with preventive measures such as planting water lilies or other floating plants that provide shade, limiting direct sunlight. Also add oxygen plants, which improve water quality and compete with algae for nutrients. It is also important to regularly remove organic debris and dead plants and change pond water if necessary.

If you do encounter an algae problem, you can address it by manually removing excess algae with a scoop net or pumping out the water completely for a thorough cleaning. After cleaning, you can restore biological balance by reintroducing oxygen plants and special pond bacteria. By following these steps, you will keep your pond clear and healthy.

Find out what it takes for an algae-free pond

Discover our planting plan for a pond without a pump or filter

Thread algae in the pond: how to control thread algae

Thread algae tend to settle in the shallow areas of the pond. They can be a persistent problem if not dealt with. One of the most effective ways to control thread algae is to place low-growing oxygen plants in these areas.

Simons advice for oxygen plants

Minimum: 1 basket with 4 plants per m²

Thread Algae Fighting Plant Filter Package - M

- For 1 - 2 m²
- 12 plants
- Placement: -1 to -20 cm


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Float algae in the pond: how to control floating algae

Controlling floating algae

Floating algae can quickly make your pond water murky, but can be easily controlled with the right oxygen plants. These plants absorb nutrients, giving algae less chance to grow. For effective control of floating algae, you can place loose oxygen plants in your pond. These plants also help regulate CO2 levels in the pond, keeping the water clear and healthy.

Simons advice for oxygen plants

Minimum: 5 to 6 loose oxygen plants per m³ (1000 liters of water)

Loose Oxygen Plants Set

- For 500 - 1,000 liters of water
- 16 plants
- Placement: loose in the water

Original price was: 75.00.Current price is: 69.95.

In stock

Are you suffering from algae in your swimming pond, plant filter or swamp filter?

Our selection of oxygen plants offers the perfect solution. Algae thrive in sunny spots and in water high in nutrients, such as fish excrement. They compete with aquatic plants for the same nutrients. By placing low-growing oxygen plants in your filter zone, you ensure that these nutrients are absorbed by the plants instead of the algae. Thus, you make the habitat for algae a lot more inhospitable.

Frequently asked questions about algae, filamentous and floating algae

Pond Advice

Algae or seaweed is an umbrella term for several groups of simple organisms that use sunlight as an energy source, producing oxygen, or O2, through which photosynthesis occurs. Algae are similar to plants in this regard. The difference between an alga and a plant is that alga does not contain roots, stems and leaves.

Although algae are generally considered simple plants, they belong to more than one realm, namely the plant and protista. Algae can be both unicellular and multicellular organisms and take complicated forms such as seaweed, for example.

Thread algae itself is not harmful to your pond, but if there are too many nutrients in a pond, thread algae can grow so fast that they can overgrow almost everything. Therefore, it is advisable to keep filamentous algae in the pond contained.

Thread algae and aquatic plants share the same nutrients. When aquatic plants use these nutrients, there is less left for the filamentous algae to grow from. Because of this, aquatic plants can help limit the growth of filamentous algae in the pond.

Aquatic plants are essential for a healthy pond environment. Oxygen plants, Sumpfpflanzen and water lilies are especially essential. These plants filter the water and add oxygen. Buy water plants at water plant nursery: van der Velde Waterplanten.

Simon van der Velde

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What is filamentous algae?

Thread algae, also known as filamentous algae, is a type of algae found in ponds and other bodies of water. They are long, thin threads that stick together and form a dense layer. This can give an unsightly appearance to the pond and affect water quality. Excessive growth of filamentous and floating algae can reduce oxygen levels in the water, which can be dangerous to pond fish and other aquatic organisms in the pond. Fortunately, thread algae can be controlled by properly landscaping the pond by adding enough oxygen plants to the pond and using pond substrate as the foundation of the pond, also add pond bacteria to the pond water. For more information, check out our pond planting plan.

What does filamentous algae look like?

Thread algae is a type of algae with a thread-like structure and looks like long, thin threads that are tangled together and can form a dense layer. The color of filamentous algae can range from green to brown or even reddish. It often grows in shallow areas of the pond and can give an unsightly appearance to the pond. When there is excessive growth of filamentous algae, it can also affect the water quality of the pond and reduce oxygen levels in the water, which can be dangerous to fish and other aquatic organisms in the pond.

What is the cause of thread algae in the pond?

Thread algae occurs in the pond due to a combination of factors, including excessive amounts of nutrients and sunlight in water and insufficient oxygen plants. You know you have enough oxygen plants in the pond when you choose an oxygen plant kit from us that matches the contents of your pond. When there are too many nutrients, sunlight and not enough oxygen plants in the water, these are factors that stimulate the growth of filamentous algae and all kinds of other algae and cause them to expand rapidly. To keep sunlight out of the water surface, it is essential to add some water lilies to the pond, as their leaves block sunlight. Also, lilies are the perfect hiding place for all kinds of pond animals, which also directly promotes biodiversity in your garden.

Removing thread algae from the pond?

Is your pond already constructed and you are suffering from a filamentous algae infestation? Then try to restore the balance with good bacteria. These single-celled organisms ensure that string algae have less chance to grow. To combat filamentous algae with pond bacteria, use our in-house developed product: Bacta Clear. A product with a unique formula, consisting of two different strains of bacteria. When administering Bacta Clear, the bacteria attach themselves to the pond substrate. The enzymes secreted by the bacteria filter the water. In this way, the water in the pond returns to balance and the filamentous algae no longer have a chance to grow. By the way, most ponds are filled with tap water. Unfortunately, this does not succeed in controlling and removing string algae, because tap water contains a lot of lime and lacks the right bacteria.

What is floating algae?

Float algae, also called phytoplankton or water bloom, is a type of algae that can occur in all types of ponds and can turn the water a murky green color. These algae float freely in the water and can multiply rapidly under favorable conditions, such as warm weather, plenty of sunlight and nutrients in the water. When they grow excessively, they can turn the water cloudy and green, preventing sunlight from penetrating the water properly. This can lead to lack of oxygen in the water and health problems for pond fish and other pond animals. It can also stunt the growth of aquatic plants. To prevent or reduce floating algae, it can help to limit the amount of nutrients in the water, maintain adequate water circulation and oxygen levels, and use plenty of aquatic plants that remove nutrients from the water.

How do floating algae form?

Float algae don't just appear in your pond. The biological balance that is supposed to be there is disturbed, and that provides an opportunity for these and many other types of algae such as filamentous algae. There are several factors present in the pond that need to be in balance with each other. If this is not the case, the clear water turns into an opaque green mush. This often occurs in improperly or newly constructed ponds, where the balance has not (yet) been found. The most important factor to keep an eye on if you want to control and prevent floating algae is: Oxygen plants. Make sure you plant enough growing oxygen plants in the pond. They absorb nutrients from the water, preventing floating algae from using them and thus preventing their further development and eventual death.

What can I do about floating algae in the pond?

Introduce enough CO2 into the water. You do this by placing different types of aquatic plants, which release CO2 into the water at night. Think pikeweed or Sumpf schwertlilie. And also choose plants that take CO2 from the air, such as water lilies and Sumpfpflanzen. Another option is to add, for example in spring, good pond bacteria that promote the amount of CO2 in the water.

How to get clear pond water quickly ?

For fast and clear results, it is important to add pond bacteria to the pond water. Bacta Clear contains 2 different types of bacteria that ensure that the pond water becomes and remains clear. This is also important for the start-up of the pond. Simply add Bacta Clear 2x a year to the pond water by pouring the bacteria directly from the bottle into the pond.


Diatoms are a type of algae found in freshwater and saltwater environments, including ponds. They are often seen as a positive presence because they serve as an important food source for small aquatic organisms and produce oxygen through photosynthesis. Diatoms are recognizable by their glass shells, which consist of silica and come in a variety of shapes and sizes. In the pond, diatoms are often present in small numbers and have little effect on water quality. In some cases, however, diatoms can multiply in large numbers and cause what is known as a "bloom." This can negatively affect water quality and lead to murky water and oxygen depletion in the pond.

Diatoms occur

To prevent a diatom bloom, it is important to limit the amount of nutrients in the water and have a good balance of aquatic plants and bacteria in the pond, these factors are essential to keep diatoms in check.

Blue-green algae

Blue-green algae

Blue-green algae, also called cyanobacteria, are bacteria commonly found in freshwater, such as in ponds. They can be recognized by their blue-green color and usually float in large groups on the surface of the water. However, blue-green algae can produce toxins that can be dangerous to humans and animals. Excessive growth of blue-green algae can occur when there are too many nutrients in the water, such as phosphates and nitrates, and high temperatures and low water circulation. A bloom of blue-green algae can lead to oxygen depletion in the water, fish death and health problems in people and animals who come in contact with the water.

Preventing blue-green algae

To prevent a blue-green algae bloom, it is important to limit the amount of nutrients in the water by planting enough aquatic plants in the pond. It is important to choose aquatic plants with different functions. For example, oxygen plants add oxygen to the pond water, Sumpfpflanzen filters the pond water with their roots, and water lilies, with their large leaves, provide shade in the pond, reducing water heating.

How do I control algae in the pond?

Instead of asking yourself how to fight algae, you could also ask yourself how to prevent algae. You can save yourself a lot of misery with the following tips:

  • Make sure the water does not heat up too much. Pay attention to the placement of the pond and put water lilies in the pond.The large leaves of these beautiful pond plants reduce the sun's ability to warm the water.
  • Provide plenty of oxygen plants.
  • Ensure adequate water hardness; algae grows well in soft water.
  • Remove incipient algae growth from the pond manually, this will make it harder for the algae to spread.
  • Make sure no leaves fall into the pond in the fall. When these leaves decay in the pond, they provide food for algae. A simple way to prevent this is to stretch a net over the pond in the fall.
  • Make sure there are not too many fish in the pond. Too many fish produce too much waste, which also makes the pond water more nutritious for algae.

Controlling algae in the pond

A good biological balance reduces the chance for algae to proliferate in the pond. A good biological balance depends on a number of factors. This starts, of course, with proper pond construction. Simon has developed a roadmap with the 4 most important points for pond construction and the 6 most important points for pond design. By paying attention to the right location, depth and planting and adding bacteria at the right time, you will no longer need a filter or pump and the pond will keep itself in balance.
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Tips, advice and substantial savings
I would like to share my experience with you, and advise you to solve any pond problems and reduce pond maintenance. As a result, you can easily save hundreds of dollars.
Tips, advice and substantial savings
I would like to share my experience with you, and advise you to solve any pond problems and reduce pond maintenance. As a result, you can easily save hundreds of dollars.
Tips, advice and substantial savings
I would like to share my experience with you, and advise you to solve any pond problems and reduce pond maintenance. As a result, you can easily save hundreds of dollars.
Tips, advice and substantial savings
I would like to share my experience with you, and advise you to solve any pond problems and reduce pond maintenance. As a result, you can easily save hundreds of dollars.