Update, since i have no corals left now i decided to do a full blackout for 7 days. No water changes during this period and reduced feeding amounts, the last 2 days(Aug 12) i also added chemi clean. On Sunday i turned the lights back on, the algae receded. On Monday i noticed that it already started to regrow, it looks similar to this:
I also gave a sample to a friend yesterday to look under a microscope and he said it looks like Dino. So i guess my next step is now trying H202 during a blackout if that doesn't work look at using metro. I read Jennc comments but i have also read conflicting comments stating no water changes should be done during treatment.
I'm not familiar with the Redfield ratio, i'll have to read up on that. I did read that increasing No3 does play a role as well.