K Rating

[Monte455]

I have been running 20k lights for some time now, but notice they do not support anything green (algae, macro algae, etc), also wonder if this has caused some of my purchases not to survive, anyone know if the 20K MH spectrum is known for not supporting green life? Would I be better off running 10K to 15K bulbs? Noticed this because of moving halemeda from sump 6500K to main tank 20K died off within a week, appears the green surface just fell off and left the white skelton, not a tank issue cause the sump algaes are doing great, only when moved to the 20K light did they appear to wither and die.

[Doodaa]

I can't tell you about the light, but I will say the halimeda dying off in your DT is probably a good thing...it grows and spreads pretty fast and even though you like what it looks like now, it will turn into a pest for you. Yes, it's easy to pull out and all, but it's just one more thing you have to do that I personally don't want to do.

[Ninong]

It could be that such a drastic sudden change (going from 6500K to 20,000K) was a shock to your Halimeda. Since they're green, they obviously contain chlorophyll as a photosynthesis pigment. Not sure if it's -a, -b or -c but all three have absorption peaks in the blue and in the orange-red regions of PAR. I think green algae has chlorophyll-c but I'm not sure on that. If so, it peaks slightly more to the right on the PAR scale than either -a or -b, which would make a typical 20,000K metal halide lamp not nearly as good for it as a typical 6500K lamp. Believe it or not, most 6500K lamps also contain quite a lot of blue. We just can't see it because of all that green, yellow, orange and red.

In any case, I think your Halimeda suffered shock and maybe the shock was related to the change in light. Maybe. Or maybe it just went sexual?

[charlie]

Stole the thought right from me Ninong, I was gonna ask if he acclimated the halimeda, that had to be close to a real culture shock!!!!