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Algae in the pond or in the aquarium is usually quite normal. But if they get the upper hand, action must be taken. Chemistry is not always necessary for this, home remedies can also be used.

In a nutshell

  • Preventing algae is possible with simple measures
  • Home remedies can help, but they can also hurt
  • the correct application is particularly important when stocking fish


Prevention is better than cure - this also applies to algae. A small amount of algae bloom in the garden pond during spring is perfectly normal. However, if this does not subside on its own within a short period of time or if the amount of algae is getting out of hand, you have to change a few other factors.

  • Planting: When aquatic plants or the plants in the bank area decompose, the water is enriched with nutrients and decomposition products. Therefore, too many plants can lead to excessive algae growth. Too few aquatic plants, on the other hand, are also detrimental to the water quality. Appropriate planting is therefore important, but dead parts should be removed from the water immediately.
  • Filter: Special filters with UV light can stop algae growth in the pond, since every floating algae is sucked through the filter and killed and filtered out by the UV light.
  • fish stock: Whether in an aquarium or garden pond - there should be at least one liter of water per centimeter of fish length. A maximum of 60 centimeters of fish should therefore be placed in a 60 liter fish tank. You should also take into account that fish grow and reproduce. It is therefore better to take the final size into account and choose a smaller number than would be possible.
  • Light: Especially with aquariums, care must be taken to ensure that it is not in direct sunlight. Sunlight drives the growth of algae. When creating a pond, make sure that it is at least partially shaded, for example by a nearby tree or hedge. In summer, a parasol can also be set up to partially shade the garden pond.
  • Cleaning: Manual or mechanical removal of the algae makes sense both in the aquarium and in the garden pond if the quantity gets out of hand. In the pond, this can be done with a landing net. In aquariums, you can also remove loose algae with a fine-mesh net. However, it is also possible to remove them from the discs with a magnetic scraper.

PH value

The pH values in the garden pond and aquarium should be between 6.8 and 8.2. These can change during the day and are usually lower in the morning than in the evening. However, this is not a problem, but an indication that there is a biological balance in the body of water.
If the algae infestation increases too much, you should check the pH value. Because too high a value can be the cause of the spread. The required test strips for the control are available in pharmacies, for example, but also online or in specialist shops.


The lactic acid from fresh whole milk is said to be able to kill algae, as it supposedly has a positive effect on the pH value of the water. The problem, however, is that in addition to lactic acid, it also contains fats and other nutrients and makes the water cloudy for a long time. In addition, the effect has not been scientifically proven.
Milk is therefore not suitable for biologically combating algae infestation.


As with milk, you can use vinegar or citric acid to lower the pH in your garden pond or aquarium. However, you need to pay very close attention to a few factors:

  • strong dilution, maximum one part vinegar to 2500 parts water recommended
  • Dilute even more with vinegar essence
  • Check the pH value of the water immediately afterwards and then at regular, short intervals

baking soda

You can definitely use baking soda to remove algae from stones or the pool wall, for example. For example, it is ideal to make a solution of baking soda or soda and water and spray the affected areas with it.
For garden ponds and aquariums, on the other hand, the agent is only suitable for combating algae if the animals have been removed and the water drained. After that, you need to thoroughly rinse off the remnants of the solution.

Notice: The mixture should consist of about 20 to 30 grams of baking soda and a liter of hot water and should be allowed to act on the algae coverings for about an hour before rinsing it off.


Peat can also be used to lower the pH.

  • Place peat in burlap bags or other permeable but close-knit fabric
  • Hang the peat bag in the water
  • leave in the water for at least a week
  • Check the pH to avoid acidification

oak branch

This home remedy for combating an algae infestation may seem strange at first, but it is effective and particularly easy to use in the garden pond. All you have to do is place the branch of an oak tree on the bottom of the pond. The advantages, on the other hand, are numerous:

  • tannins contained in the bark are biological
  • pH of the water is lowered
  • comparatively slow release
  • the water is slowly acidified, which is gentle on all aquatic life


In aquariums, for example, shrimp, snails and catfish can control the amount of algae. Snails and catfish can also be used in the pond. However, you must select the animals to suit the prevailing temperatures.


Plants fulfill important functions - both in the garden pond and in the fish tank. On the one hand, you can clean the water. Water hose and water plague, for example, are suitable for this, and they also spread comparatively quickly.
For shading, for example if you have created the pond in a very sunny area, you can bring in plants with large floating leaves. These have several advantages.

  1. They darken some areas of the pond and thereby reduce the spread of the respective algae species.
  2. The plants consume nutrients and therefore reduce the possible surplus in the water, eliminating the basis for the algae infestation.
  3. They offer protection to aquatic life and create different temperature zones, which is positive for both algae and fish and the like.

water change

Another way to combat or prevent excessive algae infestation is to change the water regularly. This applies both to the garden pond and to aquariums. However, you must note that you must not change filter materials and water at the same time. Otherwise the bacterial balance is disturbed, which affects both plants and other living beings.

frequently asked Questions

What is the connection between the amount of water and algae infestation?

The more water there is in the pool or garden pond, the more stable the biological balance. Aquariums and ponds should therefore always be set up or selected as large as possible.

What role does the design play in the garden pond?

If there are deep water zones and a stepped riparian zone, the temperatures within the pond are very different. As a result, algae cannot spread so easily. In addition, various animals can settle in the garden pond.

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