however the topic of this thread is led spectrum vs halide spectrum.
The title of this thread is "
6500k T5 Bulbs - Important Spectrums Missing in LEDs?" Not if Halides give better growth or not. Th OP refer to the RGB trick of T5 bulbs. Some people start to discuss halides instead - showing pictures of superior growth. I only post one video and one picture of very good growth below LEDs. And if you look at the spectrum - a 6500 K white LED is more similar to the Halides spectra compared with "white" T5 bulbs that have three spectral tops.
What is it about the leds that you would give them the nod on better performance? Not talking about budget or cost of operation. But what about the spectral quality, intensity, and coverage do you believe is responsible to the improved results?
Photons are photons whatever they come from. However the proteins that catch the protons works optimal in certain energy levels - the catching is a quantum process. LED fixtures can be designed just to emit the needed energy quantum that you can express like this E = h*c/λ. The energy quanta of a photon is inversely proportional to the wavelength of a photon. If you know the energy quanta a certain protein need in order to catch energy for the photosynthetic process (and transform/transport the energy quanta to PS2 and further to PS1) you can tailor your LED array to do a maximum work with minimum energy input. However - today many manufactures work much with white phosphorous LED that IMO transfer the spectra of the LED to something like the metal Halides - the technique for white T5 bulbs does not do this - instead they use blue, green and red in order to create a "white light"
In my aquarium - I use a fixture that include RGB LEDs and I run my reds at 100%. It include 4500, 6500 and 8000 K LEDs too, I use them during "High Noon" and minus - plus 2 hours. The setup include greens too.
The large Acropora was grown under a combined type of LEDs including fixtures with much red and green (Green House LEDs) but also pure Blue/white fixtures.
In my home aquarium - I do not run white LEDs (or run them very low) during evenings but I still look at something that looks like a white aquarium. That´s because of my RGB chips that tricks my brain. It tricks my brain but does not dazzle weak light sources such as coral fluorescence as lumens strong white LEDs do. I get better colours too - even better reflected colours! I do not looks into a blue hell - it give the same favors to me as modern T5 bulbs. I have 9 channels to adjust in my fixture and have add a custom build far red fixture too.
It is not a surprise that LEDs will hurt corals at lower PAR than metal halide because the PAR definition cover all photons between 400 - 700 nm not the radiation that the photosynthesis can use. The LEDs will give more of its radiation in wavelengths that the zooxanthela can use compared with the MH. It gives more PUR.
Yes - MH is history sooner or later - its time is gone. The name is technical evolution and it is our luck that this exist. If it not have exist (technical evolution) I had to write down this message, get down to a telegraph station - they send it by morse to Grimmeton south of Gotenburg - they start the generators and send a LW message to New York and a telegram boy pick it up and deliver it to each of you.
Sincerely Lasse