Krzysztof,
Let me write what I understand from your answer. Maybe I understand what I'm already convinced of missing what You are trying to say.
Water quality is fundamental to achieve health, growth and colour. Without that We can't reach those results, independently from nutrients level.
The more the inorganic is low, the more bright and vivid will be coral's colors, but they must not be absolute zero, otherwise they will loose intensity. Through the use of All in one BP, flow regulation of their reactor and quantity of administered food, You keep nutrients always available.
Luca
Yes, Luca, you understood me very well.
I've always been very impressed your your reef(s). Well done!
Thank you for you kind words, hope you will follow my thread.
Krzysztof