how much does this type of LED affect the coral color?
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how much does this type of LED affect the coral color?

I don't think the cause and effect you're assigning to ~420nm light are tightly linked, if at all. From my understanding, that curve represents something like the "able-to-be-used curve" and not much more. There are lots more factors to get all the way to coral growth....where UV light (see earlier link) doesn't generally seem to make much difference.
-Matt
I've been experimenting with the "able-to-be-used curve" for over 5 years. Corals are found in varying depths which affects spectrum...They are highly adaptable provided proper acclimation.
The main reason to go all LED over MH/LED or LED/T5 is cost, efficiency and longevity.
For the price the XT-E Royal Blue is King of Growth.
I base this on the Intensity per Watt and all reasonably priced UV 410-430nm are much dimmer and produce much less PAR. The 450nm Royal Blue is about 60-80% effective but two to three times as bright. The math is easy and growth is proven.
This is just my personal experience growing SPS frags.

