Calcium levels are also a factor of course, especially for small polyp stonies.
Two main things make my coral visibly popping with health right after I do them. One thing is a good water change along with fresh carbon (filter sock) + changing out phosar when needed (filter sock). The other is when I feed a pinch of golden pearls (50 to 100 micron) along with my regular feeding (usually plankton). Small "shrimpy" foods or blended fish scraps can be swallowed by coral polyp mouths for sure, but when I feed golden pearls the corals all turn into little vacuum cleaners so to speak, opening eagerly to 'filter' the food out of the water. The 'micro' foods are so small that the fish don't 'get to them first', and they stay in the water column for quite a while. There are other 'mirco' coral foods available that probably have the same effect.
Its difficult to feed enough if you are having algae problems though of course, which many of us go through or are wary of so we try to cut back on feeding to help solve or prevent the problem. You have to be careful using golden pearls and other 'micro' foods since they can cause nitrate spikes.. a little zoo plankton goes a long way. Thats a reason many non-photosynthetic filter feeding corals can't be kept easily in most setups - you usually can't bomb the tank with enough zoo plankton for them without crashing your tank / causing algae outbreaks.
http://www.brineshrimpdirect.com/other-goldpearl-particle-c149.html
Like some of the people with 400watt bulbs said , you can usually get away with higher kelvin and still get good growth since the output is so high on 400watt bulbs. Many people run 20k/radium bulbs on their 400w setups and get good growth.
The reason I was promoting the lumen brights is that they get more par out of a bulb, and across more of a tank width and depth, even with 250w bulbs let alone 400w. However most people have to redesign/mod their canopy since the lumen brights have to be mounted so that the bulb is 15" or 16" above the water surface for the proper effect from the reflector. These reflectors also penetrate the tank with so much light that new owners have to start the new setup with a one to two hour MH acclimation photoperiod for many weeks so that they don't bleach their corals. They then ramp it up to 3 or 4 hours, and eventually top out the MH photoperiod at 6 hrs max from what I've read. People are raving about how their tanks look lit with these reflectors, and are also commenting on better coral growth with shorter MH photoperiods. Many people are running 12k reeflux bulbs on them too, which would probably be a lot more pleasing to those of us who don't like the look of 10k bulbs.
I like the color of my 14k DE pendants on my 120g tank , which burn more like 12k since they are brighter DE's. I get good coral growth as long as I am vigilant about water changes + carbon,run phosar, feed golden pearls periodically, and dose kalk. I've decided to go with three lumen bright mini reflectors on my next tank though. Don't confuse the name "mini", they are only small in comparison to the large lumen brights.. 16" diameter vs. 20". The tank they are going on is 60" x 30" x30". I'm going to set it up similar to melev's reef though he uses 10k's on the ends usually... The setup will be 250w SE 12k .. 400w SE radium .... 250w SE 12k. I also have four 4' vho's I may install as 'side rails', two on each side of the central MH, using 14k VHO bulbs. I'll have to let you know how it goes in the future, but I'm staying away from 10k bulbs. I'll have a decent photo period with only 14k vho's for awhile though because as I said you have to be really careful and acclimate corals to the lumen bright lighting setups over a few months at least. The need for acclimation will be exacerbated by the fact that the bulbs will all be new so in an over-bright burn in period also.
I do like the 14k (12k) reefoptix DE pendants on the bluewave VII hqi dual ballast I'm running on the 120g reef right now, but I am going to sell it after the new setup is running in order to make up for some of the cost. They do sell lumen bright DE pendants also if anyone is interested.
