(Bio)³

Thats what I was thinking esac. When I went from 400 Mh to 1 BML 4 ft I got diatom blooms, cyano blooms and coral stretching for light. Let it sit like that for 6 weeks then went back to MH and the cyanodiatom is gone in 3 days and all coral are back to squat and happy

Yes, if the lights are changed and the corals are expanding a lot more they are looking for more light. The cyanodiatom bloom is from the drop in intensity (but in other situations can be from increase)and would happen whether it was LED, T5s or MH used (ie. 250W to 150W) and the cyanodiatom is still there it's just being outcompeted by the corals. In my experience most algae problems will dissapear on thier own but it usually takes months to work through the cycle.

Well 6 weeks of diatom/cyano was enough to make me pull the BML fixture off and put the MH back on. diatom/cyano both went away in 3 days of switching back. Maybe the BML is more algae growing spectrum than my MH? I dunno but I do know the fix