The "glow" you see from photos on the net are usually from photoshop software editing and has little to do with natural colours. However using actinic bulbs [not powercompact] can produce the ultraviolet colour enhancement you are expecting. From my limited observations, the brown corals are showing a healthy colony of zooxanthella, but adding more light will reduce the need for the algae culture and they will thin out leading to a more transparent tissue. This appears either white [calcium skeleton] or with the actinics, subtle flourescence. 250W halides are good down to about 12"-16". Why not move something brown up to the water surface & see if it changes into what you want? If yes, then spend more money & upgrade. 20,000K will certainly look blue just like real depth in the ocean, but colours also disappear. If you have seen real life items you like ask the caretaker, most of us love to explain to an admirer.
