PAR readings vs the nanometer of blue light

[ZoWhat]

Trying to understand what PARs to hit with what spectrum of blue vs purple light....

So in general I understand this to be true about PAR and Zoas:

Zoas requiring Higher light = PAR 150-180
Medium = around 100
Low = around 50-80

QUESTION though:
....these PAR readings are taken with what nanometer of blue light peaking? (For those who have control what nanometer of blue to peak)

420-purple?
450-blue?
480-bright blue?
500-cyan?

Example:

maybe I can push 150 PAR but the light peak is a hard purple intensity 420nm. But at the same time my 480nm bright blue is at 75 PAR.

Would you consider that "high PAR lighting" having two PARS for two colors of blue/purple?
.

 

[Doctorgori]

I sorta get the jest of your question….
I also wonder if corals can use alternate wavelengths if there isn’t enough peak in the bandwidths they like…
I’ve grown corals under redder wavelength energies with a lot less blue in the spectral chart (if available)

 

[DrZoidburg]

I guess it would depend on brand of par meter, led or t5 fixture, and amount of each type of led's . For par meter I have has a correction factor. Reads x amount but is actually maybe 10% brighter than par readings for a particular blue. It is different correction factors for different led colors.

 

[redfishbluefish]

You don't want to know PAR, you want to know PUR (Photosynthetically Usable Radiation).

THIS LINK explains the difference, and the example of green light, which could offer loads of PAR, but very little PUR

 

[Daniel@R2R]

I'd love to see someone like @Dana Riddle or other #lightinggurus weigh in on this.

 

[Hooz]

Curious which zoas anyone has found that "require" high light. I've found that certain ones wil adapt to higher light, but they all seem to do well in lower light for me (60-80 PAR).

I run LuxEngine LED pucks in my Prime HD lights (6 lights, 3 tanks) for an improved, fuller blue spectrum. This is the spectrum (Lux Optimized 3) that I run for my tank(s):

Growth and color for my zoas has been pretty stellar.

 

[Dana Riddle]

I see a couple things inferred here, perhaps I'm reading the posts incorrectly. First, the energy of the photon (violet higher than blue, blue higher than red and so on) doesn't matter in photosynthesis. Once the photon is absorbed by chlorophyll or other photopigment, it becomes an electron. Photosynthetic Photon Flux Density (PPFD, or PAR) reports all wavelengths as being equal in units of micromol/m2/second - of course, this is not actually the case. As some have mentioned here, it is Photosynthetically Usable Radiation (PUR) that we might be interested in. However, in some experiments I performed years ago with the stony coral Porites, we found that growth rates (as determined by weight of the fragment) were highest under violet/blue light, but it was statistically insignificant, and the growth rate was due to a factor other than light. That's where the project ended since my lab specializes in lighting. Other lights used were mixes of LED mimicking sunlight, 20K, etc. In a nutshell, PUR seems secondary to PAR when we're using lights designed for reef aquarium use. Now, as for zoanthids. I was invited to view a fellow tanks about 2 years ago, and he specialized in zoanthids. He had marvelous tanks where PAR maxed out at 100, and measurements of 50 were common.

 

[Hooz]

So the thought would be to get as many usable colors in the mix as possible (violets and blues in our case), then just adjust the overall PAR accordingly.

At least that's what I get from what @Dana Riddle just said.

 

[Dana Riddle]

So the thought would be to get as many usable colors in the mix as possible (violets and blues in our case), then just adjust the overall PAR accordingly.

At least that's what I get from what @Dana Riddle just said.

It's really a matter of personal preference, although I wouldn't recommend using a lot of red light (perhaps no more than 15% total). Zoox photopigments will adapt to different light spectra by adjusting amounts of photopigments in a phemon called chromatic adaptation (up to a point of course). Once photosaturation is reached (usually around PAR of 300-400) light quality isn't much of an issue since photosynthesis will not increase with increasing light intensity.