Hi Erwi
Hi Erwin,
Sorry to bang on about the ferts and BBA bit but the iron part is actually something I picked up in another artical. Please find link below:
I'll try upload photos today 😊
I see that the website is advocating the 'nutrient imbalance' = algae theory. I prefer not to add to the rich and colourful discussion of "nutrient imbalance theory" that can be found in this and other forums.
In planted tanks, you often have beard algae when there is an imbalance of micronutrients (trace elements, especially iron). If you already use an iron fertiliser, you ought to reduce the dosage. Measure the iron content of the water with a water test. It ought to be at around 0.05 to 0.1 mg/l.