Fighting threadals in the pond »How to get rid of them

How to recognize thread algae

Algae are present in every garden pond. The most common ones, however, are blue and green algae, which can hardly be seen because of their microscopic plant bodies. They also pose a relatively minor threat to water quality.

The thread algae, botanically Zygnema, are much more problematic. This is a whole genus within the green algae. Therefore, you can visit your pond in different forms. For example as:

• Long, branching, green threads
• Furry, wad-like coating on the surface of the water
• Clumps that also overgrown stones

The problem with thread algae is that they grow at low water temperatures from 5 ° C and can spread very quickly. This increases the risk of rapid water clouding. If you do not act in time, the algae bloom quickly and the pond threatens to tip over. The rapidly developing algae mass then soon dies due to the nutrient depletion and sinks to the bottom.

The algae residues consume a lot of oxygen, which can cost the lives of fish, insect larvae and amphibians. The sunken algae on the pond floor then release nutrients into the soil and water again, which can lead to new algae growth.

What can be done against the thread algae?

Preventive measures

In order not to let it get that far in the first place, you can do a lot in advance. Basically, the best preventive measure is not to let the nutrient content in the pond water get too high. You can do this by:

• Regularly fish the fall foliage from the surface of the water
• Plant many pond plants for nutrient utilization - they deprive the thread algae of the basis for settlement
• Do not overfeed any fish stock - excess fish food unnecessarily increases the phosphate and nitrogen content in the water!
• Interrupt possible lanes of (fertilized) flowerbeds into the pond water
• Put algae-eating fish in the pond: silver carp or grass carp, for example, are willing to destroy thread algae

Acute care

If it is already too late and thread algae have settled in the pond, preventive measures will of course no longer help. Now we have to act acutely, because as I said: Filamentous algae grow immensely quickly and will soon take the whole pond under their control.

First of all, it makes sense to fish off the thread algae, which are quite clearly visible and somewhat coherent, with the cashier. If you recognize the infestation at an early stage, you can perhaps get the curve around and slow down the spread.

If the infestation is already advanced, algae killers may have to be found. However, if possible, they should only be used in an emergency and have no lasting effect. Algae killers cause the algae to clump together, making it easier for a filter pump system to remove them from the water. UVC lamps also have the same effect.