Thread algae live in almost every pond, which is quite natural. But if they get the upper hand, they can severely disturb the biological balance in the garden pond. But what to do?

In a nutshell

  • to effectively combat the causes of the imbalance in the pond
  • approach the causes by checking the water parameters and water quality
  • pH value is an important indicator for the water quality in the garden pond
  • Control methods include pH reduction, fishing, nutrient deprivation, and use of natural algae eaters

methods of combat

Here we present 13 promising methods for removing thread algae in the pond:

Mechanical-technical methods

With landing net

Fish off filamentous algae with a net
  • first action is fishing
  • with net, thicker stick or special brushes
  • Dip the stick and remove algae by rotating it
  • Landing nets should be fine-meshed, with a net that is not too deep
  • use brushes in difficult places
  • coarse-toothed rake unsuitable
  • could damage the pond liner
  • Dispose of fished algae on compost

With mud sucker

  • Removal of filamentous algae floating freely in the pond and those adhering to stones and soil
  • Bottom sludge is sucked off and aerated
  • Be careful with fish, snails and other pond inhabitants
  • store the removed mud near the pond for one to two days
  • sucked microorganisms find their way back into the pond

Tip: Purchasing a sludge sucker is worthwhile for a pond size of 20 square meters or more.

Using a skimmer

Skimmers in the garden pond
  • so-called floating or standing skimmer
  • remove thread algae and impurities from the pond water surface
  • suck up material before it can sink to the ground
  • Floating skimmers have floating bodies
  • they adjust to the water level
  • Stand skimmer firmly fixed to the pond bottom
  • Adjustment to water level over swimming caps

Adjust pH

Through substrates containing humic acid

The pH value plays a crucial role in water quality. Ideally, it should be between 7 and 7.5. If it is too high, this favors the growth of thread algae.

  • Substrates containing humic acid promise help
  • untreated peat, bark mulch, oak bark or oak leaves
  • Fill the substrate in a close-meshed net or jute bag
  • Attach cord for removal
  • hang in the garden pond
  • contained humic acid can get into the water
  • Net should float freely
  • replace substrate once a month
  • then hang back in the pond
  • Check pH regularly
The pH value of the garden pond, for example, can be easily determined with commercially available test strips.

Partial water exchange

In order to adjust the pH value, it is also possible to exchange around 10-20 percent of the water volume over a period of two days. Counterinfestation with the addition of environmentally friendly pH minus preparations. Rainwater must be filtered beforehand to prevent the additional entry of nutrients and dirt particles. Both methods are very effective.

Consistent nutrient deprivation

Through phosphate binders

  • Phosphate can only be removed with special phosphate binders (mineral binders).
  • Algae shouldn't be out of control yet
  • Binding agents can reduce the phosphate content in the water
  • binds phosphate
  • algae is then no longer available
  • Filamentous algae starve
  • Targeted use requires precise knowledge of the pond volume

With pond bacteria

  • Bacteria can starve filamentous algae
  • bind nutrients, loosen pond sludge and improve oxygen supply
  • convert nitrate and phosphate
  • are available as bacterial mixtures
  • Prepare the mixture according to the manufacturer's instructions, put it in the filter
  • biological decomposition of organic material is activated in the water
  • The result is a reduction in algae
  • can also be used in ponds with fish stock

Tip: Microorganisms that occur naturally in the pond but can be destroyed by improper use of UV-C lamps are also considered secret helpers.

Use aquatic plants

Crab claw (Stratiotes aloides)
  • Aquatic plants provide shade and oxygen
  • consume phosphate and nitrate
  • can absorb excess nutrients and pollutants
  • Remove excess plants from the pond
  • use nutrient-consuming, fast-growing and prolific species
  • regular thinning of the plants is important
  • consume so many nutrients
  • Algae is deprived of basis
  • only use special aquatic plant soil

Tip: About one third of the pond surface should be covered with aquatic plants such as hornwort (Cerastium), water quill (Hottonia palustris), waterweed (Elodea), crab claw (Stratiotes aloides), duckweed (Lemna) and/or milkweed (Myriophyllum).

Other methods

ensure basic supplies

  • Aquatic plants suffering from a lack of nutrients promote the growth of algae
  • Aquatic plants also need nutrients
  • can only grow so luxuriantly and compete with algae
  • one-sided lack of nutrients affects the plants
  • Algae can settle more easily

Avoid intense sun exposure

  • too intense solar radiation and heat promote algae formation
  • therefore ensure continuous shading
  • for example in the form of plants
Indian lotus (Nelumbo nucifera)
  • Aquatic plants with floating leaves are ideal
  • e.g. B. water lilies (Nymphaea), lotus leaves (Nelumbo), sea cans (Nymphoides) or frog bite (Hydrocharis morsus-ranae)
  • germ-reducing UV filter systems can also reduce algae

Remove unsuitable pond stones

  • Algae use unsuitable pond stones as a source of nutrients
  • e.g. stones from quarries
  • contain undissolved minerals and phosphates
  • are taken up by deep-rooted filamentous algae
  • just what you need for a lush algal bloom
  • Minerals dissolve out over several years
  • depending on the type and size of the stones
  • ideally use stones from rivers

Use of natural algae eaters

The sump snail is considered a good algae eater and pond water filter. The plants in the pond are taboo as long as their preferred food does not run out. The body of water should be deeper than 80 cm so that the snails can overwinter there. Another, slightly larger algae eater is the pointed mud snail, which can live up to four years. She lays her spawning strings on aquatic plants, from which up to 200 offspring then develop.

Pointed mud snail (Viviparus contectus)

Tip: The pond water for the mud snail should not be too soft, otherwise it will lack the calcium it needs for its snail shell.

Use algae killer

  • chemical preparations in liquid and powder form
  • contain algae-killing ingredients
  • Use only in the case of acute algae blooms, not permanently
  • no permanent effectiveness
  • Symptoms do not address the root cause
  • destroy structure of algae and unicellular organisms
  • Plants can be sensitive
  • consult a professional if necessary

frequently asked Questions

Are these algae harmful to the garden pond?

They are not harmful, but a necessary part of an intact garden pond. Only if they spread unhindered is this an indication that the balance in the garden pond is out of control and something needs to be done.

Are fish suitable for fighting?

Fish are hardly suitable for combating filamentous algae. With their excretions, they even provide a nutrient input and thus contribute to the formation of algae. Nevertheless, there are said to be species that eat algae, such as rudd and grass carp. When it comes to fish food, you should pay attention to the quality, because even inferior food can promote algae formation.

Is it possible to completely prevent thread algae?

No, but they shouldn't get out of hand. That's why you have to do something to support and maintain the biological balance in the garden pond. This also includes the algae, because they are not the cause of the problem, but only a symptom.

Category:

Garden design