There is zero evidence that light below 450nm has any benefit to corals. It's just bantering points pushed by people who are having trouble growing coral and picking a straw horse to blame.
UV LEDs only started showing up in fixtures when the semi conductor industry figured out how to make them reliable and cheap.. The primary market for these things is DJ lights ...not reef lights. I have a bunch of 50watt 395nm chips. They have no business on my reef tank.
The Spectrum of the sun is pretty well known and doesn't have to tested. The spectral absorption of chlorophyll is also well known. The spectral band for Clorophyll photon absorption is also pretty wide. Zooanthalae algae in corals can pretty much thrive when being hit with photons from 420nm to Windex. Higher energy , higher frequency photons with shorter wavelengths dont translate into a higher conversion efficiency for chlorophyll. As long as its blue light of any flavor it works for Zooanthalae.
Reef Halides lack violet and UVA - no problem growing coral.
Reproducing the spectrum of the sun, providing you could actually do so which is unlikely in 3m of water won't grow corals better. Zooanthalae will just absorb the same blue photons as they normally do and ignore the rest.
Put a plasma sulfur above your tank if you want to truly mimmick solar spectrum. It won't grow corals better than a black box at the same PAR.
