Thank you Tom,
I am sure it will not be hard to get rid of it when I know what it is. Unfortunately, I showed my pictures to several people and they told me that they see BGA. When I told them that BGA looks different, they told me that there is a lot of kind BGA :-( Thank you for your help again.

You are right with water stabilization and CO2 (pH). The biggest difference between aquarium and tap water is NO3 and pH. Aquarim is about NO3 10 mg/l and pH about 6,6 - 6,8. Tap water is NO3 25 mg/l and pH 7,5!

Algae grows mainly two days after water change. So, I think that pH increase a lot after water chang (CO2 lower) and I also add a lot of new NO3. After one ot two days, when pH is about 6,7, algae stop growing. It seems to be logical. I only did know the reason. I will probably build system with pressure cylinder and CO2 sensor which would keep CO2 stabilized much better then now. I will also try to optimize fertilization by mixing own PMDD.

Nice to meet experts

Petr