It takes time and persistence, every other technique is just another tool in the toolbox. There is no magic solution here. I think i see the coraline, your goal is to keep algea in check, while it spreads. Get stuff to eat the algea, manually remove the long stuff, maintain water chemistry. Takes time though( think months and years, not days and weeks)
Yes, i might have a short vision term, the tank went bad since i tried to reduce phosphate withe lanthanum chloride
The Giesemann Megachrome bulbs have more of a purple tint that some other MH bulbs. Being from Germany, they should be available to ship to France.
I'll check, love purple =)