I'm fearing that it may be too much light. Even light hungry acros turn a purpleish whit color after being anywhere close to the top.
My tank is only 24" deep, and I really think 250w with some suplimentation would work better.
The corals toward the bottom seem to grow much better. I know I could move everything down, but I want to cover the rockwork with live stuff.. not just the bottom third.
Hmmm, just last week I was talking to the owner of a "local online retailer" about PAR, lumens, and wattage on different bulbs and ballast combinations and he mentioned how he feels that once you get to 400 watts on an HQI bulb/ballast, the abundance of light starts to stunt coral growth, since the ballast is overdriving the bulb.
I wouldn't be surprised if that was the case with your tank, as you suspect also.
Since you've got a canopy, though, why not go with a retro kit or a lumenarc?
well.. i have a 3 sided canopy.. no top.. no back.. that allows me to hang a pendant and also have my 2 VHO lamps across the top.
I have a nice light setup.. its just a LOT of light.. and its a bit of a hassle to have to take the 3 sided canopy off every time I want to get to the water.
Is your light a DE or SE? Cant you just get a smaller ballast and keep everything else the same? I am under the impression that the mounts are the same for 250/400 regardless of the ends. I have never seen a 400 so Im just winging it here.