I don't know about UV
rays per say but I can tell you my observations based on kelvin temperature. The 6700K - 14000K are more of a daylight spectrum and don't show the colors off properly. These temperatures are very pleasing to the eye over all and are very bright.
If you keep any deeply colorful corals (zoanthids, palythoas, ricordia, etc..) then you want to add more actinics to balance it out. At 20000K, it gives you a nice look but not as nice as being able to simulate dawn and dusk with multiple bulbs.
fixture will give you higher uv
output compared to other lighting fixtures. This is why the daylight bulbs appears to cause the bleaching out of corals. The intensity is too strong. We also need to have a uv
protected coating/glass to filter out the harmful uv
The deeper the tank is, the more uv
rays will be filtered out of the spectrum (through the water) as it reaches the bottom of the tank. The corals that are higher up and closer to the light will produce nicer colors compared to the bottom of the tank. They will brighten up as a protection from the uv
rays striking them. Look at a shallow reef in the ocean compared to the deeper end of things.
Zoanthid corals are known to produce nicer color pigments as a protection against these uv
So going back to kelvin temperature, the higher intensity daylight temperatures (simulate afternoon time) will appear to bleach out the corals. But when you view it under an actinic light (higher in the spectrum with more colors), it is more colorful.
Okay, I am rambling on and don't even think I'm answering your question or am on topic. I thought I take a stab at this but am probably totally off.