Any updates on UV LEDs and coral? (esp. SPS)

[HuskerBioProf]

I have searched and found a lot of anecdotes in the form of people claiming high UV "fried their coral" or "enhanced their growth" or gave extra "pop." I have AI Hydra HDs and I am curious about the UV light (400 nm). The only thing I can see the UV doing is making the fluorescent corals glow more when only the UV + 5% deeb blue are on at night. Is there any good evidence one way or another about the impact of UV on coral health in aquariums? I currently have my UV maxed out on my Hydra HD (~118%) during the day, and I drop it down to 45% at night. It adds a visible violet hue and extra coral glowing. I haven't had this going on long enough to know whether it has any anecdotal impact on health. I am especially interested in SPS.

Any thoughts?

 

[Nano sapiens]

What the reef community calls 'UV' is actually not (true ultraviolet has wavelengths from 100 nm (30 PHz) to 380 nm (750 THz). 'Violet' is a more accurate term for your ~400 nm and 'Hyperviolet' or 'Actinic' for ~430nm.

These violet wavelengths do stimulate photosynthesis and they can stimulate the coral to produce certain pigments. The reason why people fry coral with them is that our eyes (and a PAR meter) are not very sensitive to these wavelengths, so we see them as 'dim' (but the coral doesn't!), so the aquarist can make them too strong, too quickly.

 

[Ron Reefman]

Nano sapiens, excellent answer, direct and to the point.

I'd also add that true UV doesn't penetrate salt water very well. Blue penetrates very well, but as the wavelength get shorter into UV territory it gets blocked very quickly. So your corals are not accustom to 'seeing' much if any true UV except for those in very shallow water.