LEDs - Well, this is interesting

[Ron99]

Originally Posted by mike31154

UV comes in different flavours(wavelengths), A,B,C. You probably don't want to be exposed to UVB or UVC for any length of time due to the potential health risks. Manufacturers of light fixtures available to the general public are no doubt keenly aware of that. Legislated marketing... The point is, Kessil does provide some UV which is generally acknowledged to aid certain coral growth.

Yup. UV A is from 315nm to 400nm. So at 390nm Kessil is just barely into the UV A range. Most others have violet in the 405 to 420nm range. My point is that I'm not convinced 390nm spectrum makes that much difference for corals vs. say 410nm. The absolute output in the UV/True violet range appears to be higher in the Kessil lights so i think it's more a quantity vs. quality thing. i suspect that if you had more 410 or 415nm emitters and matched the output of the Kessils you may see similar results. But Kessil claiming true UV output is a marketing gimmick IMO as they are just barely in the range.