doubt it but it would be nice to know if you have been using that lighting since tank has been est. because if you were using a lower watt light then all the sudden pop that in its possible you shocked your corals. when going to a higher watt or lower you have to let your corals photo- acclimate.
The temp swings about 4 degrees up to 82 at this highest point. The pendant is about 12" up.
I believe it runs 7 hrs / day
I did go from a 250w pendant some months ago to this 400w, and I thought that that was the issue, but even some new corals I've bought seem to be loosing color.
Everything in my tank is setup very well and all the equipment is more than adequate. The only thing I can think of is that when I set it up I put crushed coral as a substrate. Maybe this stuff is fowling my water by trapping things. As a precautionary measure I think I'll start swapping it out with sand.
Have you had the 4 degree fluctuation since day one, or is that a more recent occurance? Again, my knowledge is a bit limited, but I do know that maintaning a constant temp is important. That could be the problem. Or maybe not. Others will chime in, if you build it they will come.......LOl
DE bulbs must have a glass sheild in place as they dont have the outer glass tube the SE bulbs have and so they give off harmful UV rays. Hopefully there is glass on your pendant at least. I would otherwise say the lighting is not your issue.
My temp went from 78-82 almost all summer last year. I didnt consider this to be an issue. Not ideal, but definately not an issue. I woule raise your pendant up and see if that helps. Thales for example, has His 400 SE 20K quite high above his tank (about one and a half feet?) with VHO actinic and has excellent coloration. (Forgive me for giving up your trade secrets) I keep my 250s at over a foot now days. What K of bulb do you have? Do you have any actinics?