Green floating algae Photo: Andreas Menke
Floating algae swim in the open water and lead to a clear turbidity of the water. Green and white floating algae occur. The white floating algae are not real algae but bacteria, which is why in this case one also speaks of bacterial clouding. The green floating algae is caused by unicellular green algae of the genus Volvox.
Causes of floating algae
Bacterial clouding often occurs after setting up a new aquarium during the so-called break-in period. During this time, the bacteria that are important for the metabolic processes in the aquarium develop. Since not all processes in the aquarium are coordinated, some bacteria can multiply explosively. Once a balance of metabolic processes has been established in the aquarium, the turbidity usually disappears again.
Green floating algae develop when there are too many nutrients and too much light. By reducing either factor, algal blooms are contained.
Countermeasures against floating green algae
Darken the aquarium
Green floating algae Photo: Andreas Menke
In the morning the fish are fed again. A water change is then carried out in which between 50 and 70% of the water is exchanged. Then the aquarium is darkened by z. B. a blanket is placed over it.
The lighting is switched off. After 3 to 5 days, the cover is removed and the light is turned on again. During the blackout, the fish are not fed.
The tank must remain completely dark during this time. After the filter has been darkened, the filter is cleaned and the water changed again vigorously to remove the dead algae from the aquarium.
Use UV clarifier
Floating algae are killed by UV radiation. If there is no external filter to which the UV lamp can be connected, a simple centrifugal pump can be used to circulate the water.
Since UV clarifiers also kill other microorganisms floating in the water and affect fertilization, they should only be used occasionally and with care.
Vigorous and frequent water changes
With this method, up to 90% of the water is changed on several days in a row until no more floating algae appear.
deploy predators
Water fleas and hoppers eat floating algae. However, it should be noted that water fleas and hoppers are welcome food for fish. A large amount has to be used again and again, or the water has to be passed through a special container in which there are only the water fleas but no fish. The filter should be switched off during this time, or you need a fine-meshed net as a pre-filter, otherwise the water fleas will be sucked into the filter. Alternatively, the filter without filter material can only run as a circulation pump.
Filter over peat
According to one report, floating algae do not tolerate slightly acidic water. The water can be slightly acidified by filtering through peat, if the requirements of the fish being cared for allow this.