These are best for making the florescence of your corals really pop, they do nothing for growth. Ron99 would know better than I on how the lights do this but I think the very specific 470nm spectrum prevents "wash-out" that can happen with actinic or other blue light solutions.
LEDs typically haver poorer penetration than other lights so the deeper the water gives less florescence effect.
Comparison pictures would illustrate this better but I can't seem to Google anything worthwhile at the moment.
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