I've been running 4 b+ and 4 c+ since November. Although the fixture is dimmable I ran both channels for 8 hours. My corals were growing but I lost color. Some turning somewhat pale, a purple bonsai for example lost the vibrant purple and turned a drab tan.
I have around 50 acropora in the tank and my colors really had me stumped. Some turned pale others were turning darker. Assuming the darker colors were high nutrients and not enough light I held the same bulbs and photoperiod but reduced nutrients. The pale corals became paler. Being a rookie I was stumped! Talking with another reefer, we went through my set up in great detail. He narrowed it down to too much light. If too much light then how come several acros are brown!?!
Three weeks ago I raised my fixture 3" and replaced 2 c+ with actinic, also reduced the photoperiod and started using the dimmer to hold intensity in two hour increments with peak power At 85% for 2 hours long, and low and behold The pales acros and returning to normal and the corals that darkened are now lightening. NO WONDER new reef keepers have issues sometimes!
I thought darker colors meant not enough light and/or excess nutrients. Yet again, some corals were paling. Not the case here as nutrients were not the issue. I'm assuming the corals that got darker went into some sort of photo inhibition mode. Heck I don't know. I just know that running too much light came at the expense of lost Acros and me chasing water issues that didn't exist.
I hope this rant helps someone else.