Question about Kelvins

[MohrReefs]

If I drop or raise the kelvins will it stress the corals? Right now I'm at 20k, but I may jump to 23k or drop to 15k. If I did that, should I match my current blue and white intensities that are currently on the 20k or will they need to change based on the kelvins? Or is that completely unrelated?

 

[Lasse]

More blue or lesser white - higher K - Lesser blue or higher white - lower K

Sincerely Lasse

 

[Dana Riddle]

If you're dialing in a warmer Kelvin (more red or less blue) do so very slowly and observe corals/anemones/clams closely. Red light is known to regulate (lessen) zooxanthellae densities/chlorophyll. In extreme cases, too much red can bleach a coral. In experiments I conducted with a meter that reports chlorophyll content, it became apparent that the human eye is a very poor judge of loss of zoox/chlorophyll. A coral can be technically bleached while still having a light brownish coloration.

 

[MohrReefs]

If you're dialing in a warmer Kelvin (more red or less blue) do so very slowly and observe corals/anemones/clams closely. Red light is known to regulate (lessen) zooxanthellae densities/chlorophyll. In extreme cases, too much red can bleach a coral. In experiments I conducted with a meter that reports chlorophyll content, it became apparent that the human eye is a very poor judge of loss of zoox/chlorophyll. A coral can be technically bleached while still having a light brownish coloration.

In that case would it be better to go up towards a cooler 23k?

 

[Dana Riddle]

There was study done using Acropora specimens and metal halide lights - the authors reported 14000K was best. Not sure how that paper got through peer-review, but it did (there were holes in it big enough to drive a truck through.) I had some issues years ago when I went with only actinic fluorescent lamps - there were growths of nuisance algae/diatoms within a day or two. Don't know for sure if the change in lights was responsible but I do know I didn't like the look of the tank. Personally, I like a crisp bluish-white light....

 

[blasterman]

Fiddling with blue / white LED ratios of such a trivial amount will not make corals grow better or worse because a cool white LED *is* a blue LED with just a bit of green spectrum mixed in and even lesser amount of red. The white LED technically blocks a bit of blue light due to the phosphors, but a blue and a cool white LED in the same family put out roughly the same PAR.

I do agree with Dana that suddenly dialing in a lot of red can cause some weird response issues because red/orange is a mostly foreign spectrum to an organism accustomed to growing underwater unless it's very shallow. However, 23-15k is mostly just fiddling with blue LEDs vs cool white LEDs and green light is mostly what;s constituting the kelvin change. Green light is pretty much not a factor to worry about.

 

[MohrReefs]

Fiddling with blue / white LED ratios of such a trivial amount will not make corals grow better or worse because a cool white LED *is* a blue LED with just a bit of green spectrum mixed in and even lesser amount of red. The white LED technically blocks a bit of blue light due to the phosphors, but a blue and a cool white LED in the same family put out roughly the same PAR.

I do agree with Dana that suddenly dialing in a lot of red can cause some weird response issues because red/orange is a mostly foreign spectrum to an organism accustomed to growing underwater unless it's very shallow. However, 23-15k is mostly just fiddling with blue LEDs vs cool white LEDs and green light is mostly what;s constituting the kelvin change. Green light is pretty much not a factor to worry about.

So as long as match the intensity I can just change over to 23k?