JoshO
Valuable Member
As the title implies, have we been wrong the whole time about the energy we provide our corals?
I was doing some digging, recently, into journals to better understand what is truly the optimum lighting for Acropora and stumbled across a study which assessed the influence of different Kelvin metal halides on the growth of Acropora Solitaryensis. They studied 5, 10, 15 and 20k temperatures, all with the same PAR value...guess what came out on top? The 20k...the most blue of all the spectrums. I was a little bit baffled by it as we always hear full spectrum is likely to grow corals quicker (anecdotal hobbyist evidence). So I dug a little deeper...here goes.
Light energy is in the form of waves. With the shortest, highest frequency at the UV end of the spectrum and longest lowest at the red end.
PAR is the measurement of the number of photons hitting an area in a given time frame that comes from the range of light which is considered photosynthetically available (I might have worded slightly wrong but hopefully you get the gist). There is no mention of the energy said photons provide, so here is where it gets interesting.
Let's say we've got 200 par of 420nm (blue) light and on another system we have 200 par of 570nm (yellow) light. From the way the hobby has described par these should equate to the same energy levels, correct? Wrong!!
If we go back to what I said earlier about the length and frequency of the light waves then you'll remember that I said blue are shorter and higher frequency. This means that each photon of blue light has more energy than it's friend the yellow photon.
This means that if we base our measurements purely on a par reading, and neglect to factor in spectrum, then we aren't going to be giving our corals the energy we expect!!
I was doing some digging, recently, into journals to better understand what is truly the optimum lighting for Acropora and stumbled across a study which assessed the influence of different Kelvin metal halides on the growth of Acropora Solitaryensis. They studied 5, 10, 15 and 20k temperatures, all with the same PAR value...guess what came out on top? The 20k...the most blue of all the spectrums. I was a little bit baffled by it as we always hear full spectrum is likely to grow corals quicker (anecdotal hobbyist evidence). So I dug a little deeper...here goes.
Light energy is in the form of waves. With the shortest, highest frequency at the UV end of the spectrum and longest lowest at the red end.
PAR is the measurement of the number of photons hitting an area in a given time frame that comes from the range of light which is considered photosynthetically available (I might have worded slightly wrong but hopefully you get the gist). There is no mention of the energy said photons provide, so here is where it gets interesting.
Let's say we've got 200 par of 420nm (blue) light and on another system we have 200 par of 570nm (yellow) light. From the way the hobby has described par these should equate to the same energy levels, correct? Wrong!!
If we go back to what I said earlier about the length and frequency of the light waves then you'll remember that I said blue are shorter and higher frequency. This means that each photon of blue light has more energy than it's friend the yellow photon.
This means that if we base our measurements purely on a par reading, and neglect to factor in spectrum, then we aren't going to be giving our corals the energy we expect!!
