What to do in case of floating algae in the aquarium?


I have an aquarium with 120 liters. There are 3 leaf plants, bottom gravel etc. in it. I have set it up completely new recently, including a new external filter. My water turned totally green after approx. 3 weeks. I therefore improved the water parameters, especially nitrite.

this is of course good (nitrite is very toxic for fish), however nitrite has nothing to do with algae growth.

Unfortunately I still have this green water. Can you give me advice how I can get these floating algae out of the water quickly and smoothly?

As an immediate measure, you can bind the floating algae with sera aquariaclear, they are then collected by the filter and can be rinsed out of the filter media.

The long-term approach is to lower the nutrient level (especially nitrate). This may sound paradox in case of hardly detectable nitrate levels, but the situation is as follows: In case of abundant algae growth and rather bright light, the algae literally draw nitrate out of the water faster than it it is supplied. It therefore serves as a nutrient for them, but at the same time is not present in the water anymore, and thus cannot be monitored. In case of floating algae trouble there certainly is increased nitrate pollution, since floating algae are typical nitrate indicators.

You can achieve nutrient reduction by

* reducing the number of fish and the food amount 

* abundantly adding fast growing plants (these are mainly bright green or reddish stem plants such as LudwigiaCabomba, hornwort etc., plus Hygrophila and quite a few other plants - there is a large selection!)

* generous partial water changes with water low in nitrate 

* possibly using a denitrifying slow flux filter 

* especially in case of brush algae: Using sera phosvec Granulat in the filter 

* not using care products that contain nitrate 

* creating optimal growth conditions for plants (good lighting, possibly CO2 fertilization, suitable bottom ground, etc.) 


Best regards

sera GmbH 

Dr. Bodo Schnell


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