Why don't you see reef tanks run with complete actinics then? Because they don't emit much in the way of pur. They're for looks. Most corals are found in shallow reefs. IMO
a 14-15k look will give you the best color and growth. Running to white of light will make everything look poopy but growth will be good. And vice versa.
However, it also depends on the fixture as a fixture running Cree LEDs in a 20k spectrum would probably provide better growth than a crappy led
fixture running a 10k spectrum. Nutrients, flow, feeding, stability play a very important role in growth as well IMO
. I also think that anyone who posts here is not definite about an answer as there is limited scientific evidence on lighting spectrum and coral growth. So all that said IMO
I like a 15k look as it gives you the best of both worlds
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