It has occurred to me lately that LED lighting has a complete lack of UV light.   Some UV must be  necessary for correct coral Growth for sps used to near surface conditions Has anyone  heard anything on this? LED is still early in the game as far as  long term exposure studies, but LED’s seem to work fine for me and everybody else I know.

However, SPS near the surface in nature obviously get some UV. The Zooxanthellae (or more precisely the Chlorophyll A peaks in the 410-420nm spectrum which helps feed the algae) can get this needed UV via a 420 nm light source (Chlorophyll A peaks in the 410-420nm spectrum which helps feed the algae).

Blue LED is typically 450 nm +- a few nm, not near enough to UV for some Zooxanthellae to thrive. Granted it doesn’t affect many corals in general, but there are several SPS than need the UV light to thrive. Growth rates also can be slower over time with some sps without any of the “damaging” UV at all. Go down few more feet though, to another reef zone and UV doesn’t play such a role.

There hasn’t really been a lot of time to study this in the long run I feel, and I am not affected personally right now as I don’t think I have anything affected by lack of UV. All the same, this seems like a hot topic to post.
There have been reports of some pigment loss, morphing and even “browning out” of certain SPS under LED only.

Several (most) manufacturers are now including UV chips in their LED systems, such as the new AI Vega’s, the MaxSpect Razor, the Orphek’s and others.

I always wondered why this was so, when the older HQI’s insisted on glass plates to block the UV. This is due to way too much UV from them no doubt. I think I understand all this now. I don’t have any sps corals that grow out of the tank seeking more light right now, but some people have some exotic stuff out there, and I thought this would be of interest. It would seem a simple supplemental 420 nm (not 460) Actinic fluorescent T5, vho or even a 40W may be a simple fix for those with an older LED systems or those that don’t have any UV emissions if it is desired or needed.

Does anyone have any observational experience with this, or any input for us here here? Please comment here.

Thanks for stopping in!


Since it is not readily visible, and I feel quite important,

I’d like to share a comment from a reader of my Blog on their experience with LED and UV It is quite valuable, and I thank them for their input:

“Hi Greg,

I don’t normally make to many comments but after reading your article last night I thought I would share my experience with the LED lights. I have been doing salt water aquariums as a hobby for the last 25 years so it was hard to make the switch to LED lighting from metal halides. I finally decided to put LED’s one my 180 reef knowing that LED’s did not omit UV. I ran the LED’s for about a month and half without any UV’s lighting and noticed that my corals were not as “happy” as they once were. I went to the LFS and obtained a 6 UV stunner strips and attached them to my LED’s. Within 2-3 days there was a noticeable difference in my corals, they were now “very happy” and growing at a rapid pace.

I currently have 7 additional tanks mainly frags and a few colonies. I have a 90 gallon set up and I run half metal halide w/blue actinics and the other half with LED’s with UV stunner. I get the same response from my corals out of each side except I have noticed that LED’s creates a lot more algae.

I have a 30 gal frag tank set up with only LED’s and no UV stunners. I certainly love the colors that LEDs produce with my corals but I am not happy with the growth of my frags in this tank. I have had a few of my frags even colonies start to receed and I will have to pull them and put them back into a metal halide tank to recover. All my tanks parameters are the same and are tested daily so the only thing left is lack of UV. I am a firm believer that UV promotes good health and growth. I tell my son that corals are like humans without sunlight we become depressed and so do corals and with sunlight humans love to be outside absorbing the suns rays and the corals love the rays as well.

I certainly will continue to run LED’s on my tank but I will also make sure that everyone of them have UV stunners to promote good health and growth. This is just my thoughts and experience.


Thanks Jackie!

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