Yup, beeeg diffs
is there a huge difference between running white or blue halides ?
Dunno if this fills any gaps in?
I know these metal halide lamps:
megachrome 150W blue
marketed by deltec, developed together with Giesemann Lichttechnik
It's meant to accentuate, supplement, or simulate "Reef at DEPTH" appearance. Also intended for moonlight/phase simulation if appropriately mounted, and controlled.
I suppose only useful in the latter respect, in larger tanks(2m up)
The manufacture states > 20 000K, but also rates at ~21 000K.
Meant to be used as above in conjunction
with SPECIFIC light types.
With ACTUAL CORAL GROWTH, or PHOTOSYNTHETIC stimulating in mind, you would HAVE to employ ''WHITER LAMPS''
on their own, or in addition to the 150W blue, or according to the "LOOK" you want
Those easily available in SA.
6500/10 000/12 000/14 000 K
The diff between white and blue, is easiest stated as the difference between sunlight and moonlight.
Which would you expect to grow a thriving Photosynthetic Reef under?