How much to the equation is PAR only relative to spectrum??

[ptreef]

SPS corals in question here:

Ok, Say I measure PAR with a phoenix 14k at 200......
Coral colors great to the eye and decent growth.

Now I switch to say a hamilton 14k with PAR at 220....
Coral colors to the eye are less attractive as bulb is whiter.
Will growth be alot better as the spectrum has gone more white/yellow with PAR increasing just a little?
Also will coral colors (actual colors not as seen by eye) stay the same or will they fade/lighten?

What if I go extreme and go say XM 10k....
colors to the eye will dramatically look worse and PAR will jump a lot so should growth. But will colors be lost a lot now...long term?

What determines growth.... combination of PAR and spectrum? More have to do with spectrum or PAR?

What determines coral colors.... spectrum or PAR?
Meaning will they color up better under say a radium 20k than an XM 10k?
Or will the have same color if grown under these different bulbs for say 6 mos and then both put under the Radium 20k. Will they then look about same? Or will the coral under the XM10k need time under the radium 20k to color up?

[Ron Reefman]

PAR and spectrum are tied together and can not be separated. PAR is the total amount of light you have between 400nm and 700nm. So you can have a PAR of 200 or 1400 with just one very narrow spectrum, like deep red or bright yellow and your corals will hate you and die. On the other hand, you could use all blue, get a 200-400 PAR and your corals will probably do OK. You may not like the 'windex' look of the tank, but the corals are fairly happy. So having a PAR of around 100-400 is what your corals want, but most of it needs to be blue. When you add other colors (white, red, green) you will increase the PAR but not the quality of the light the corals need most. And yes, some small amount of other colors can be good for the corals, but it's only needed in small amounts. MH bulbs have varying spectrum graphs and the look in your tank in defined as a color 'temperature', as 10K, 14K and 20K. You really need to look the the spectrum graphs.

Corals want a lot of blue, and deeper corals want almost exclusively blue spectrum (400nm-500nm). Shallow corals also use some red spectrum in the range of 650nm. The red is good for some zooxanthellae growth, but too much red encourages algae growth outside the coral, i.e. hairy algae and more. Corals only need a very small amout of any other spectrum.

Coral colors come from 2 sources, reflected light and emitted light. The reflected light is best if we see it under a full spectrum white light so all the colors of the spectrum are there to be reflected. Emitted light is made when coral pigments absorb light (mostly blue), use some of it, thus reducing the energy in the light and then emit it back out as a less energetic color like green, yellow or red. That is, they take in 450nm short wavelength light and emit longer, less energetic 500-700nm light. And these pigments are used, in part, by the corals as a sort of sun screen. So a deep water coral that has only ever seen blue light, and is now exposed to a full spectrum of light, can make new pigments and change colors, i.e. morph. So different corals will look and grow differently with different lights. Some like very, very blue, some like light blue, some like blue with a little red, very shallow corals like as much red as they do blue. Give any of them something different and they will grow different and color different.

Now you also want to look at the corals and see their colors. For our eyes, this involves having white light. White light is normally thought of as including all visible spectrum (400nm-700nm). But our eyes can be fooled. Old TV sets made all the colors with just RGB (Red, Green and Blue) tubes (or leds). Stage lighting is often done with RGB spotlights as well. So with a fairly even mix of red, green and blue your eyes will see white, but your corals will see red, green and blue. They don't have our eyes and we don't grow their zooxanthellae or color pigments.

So you need to balance what the corals need with what you want to see. Does that help any? I know it can be very confusing, I'm still learning myself. So feel free to ask questions.

[Pacific Sun RD]

@Ron
I see that you understood everything perfectly ;-)

[sirreal63]

I would add to what Ron states...that we really don't have a complete understanding of what all of the functions are in relation to coloration and growth of corals. I do not have the answers but offer some observations.

There is an article that may help in understanding, it's the best I have seen.
http://www.advancedaquarist.com/2012/10/aafeature

Fig. 2 is a great one because it shows what part of the spectrum corals receive at depth. You note that he mentions that "15m is the maximum depth at which we can still find many light-demanding corals in nature. At the depths below 20m, the number of light demanding species sharply decreases." Look at the graph and see what wavelengths are available at 15-30 meters. Those higher wavelengths are still there but are greatly overpowered by the lower wavelengths. There are still corals deeper but the majority of SPS collected for the trade are not much deeper than that. This article discusses what is collected where in Fiji and is a good representation.
http://www.advancedaquarist.com/2005/10/aafeature1

Fig. 4 shows light absorption by zooxanthellae. The text in this section is critical, coloration isn't just about light.

As Ron correctly stated there is a difference in what we see, and what the coral sees. The 10K MH bulb looks white to us but the coral sees that very heavy 420nm peak. Below are plots pulled from Sanjay's testing of the two bulbs I primarily use. I also use VHO SuperActintics which peak at 420nm and this balances out the 150 watt Radium nicely. It is amusing that we have used actintics to help how corals look to us, but we were actually giving them what they needed as well.
http://img.photobucket.com/albums/v362/sirreal63/UshiandRadium1.jpg

Yes I do get excellent growth from both but it is slightly better with the 10K Ushio, the question is why? Is it the heavy 420nm that the Ushio has that is added to greatly with the 420nm peak of the VHO SuperActintic's, is it the 545 or 590nm? There is not much difference in coloration of the corals but it appears better to the eye with the Radium and VHO SuperActintics because of the lack of the higher wavelengths that wash out the fluorescence, to the eye that is.

PAR is only a part of the equation, you also need to consider PUR and nutrition.

Something to think about, every coral you put in your tank is now a shallow water coral. You may be able to mimic the color a coral gets at 40 meters but you would not like it visually to your eyes nor would you see them the way we want to see them.

These are just observations, I do not wish to conclude they are fact but rather things that bear thought. The truth is over the years people have successfully grown healthy and colorful corals under virtually every light available to us.

[ptreef]

Wow, thanks for the input....

So ideally we are looking for a bulb that has the majority of the peaks in the 400-500 spectrum for the corals to color and grow. The rest of the spectrum really is to balance out more so for our visual appeal?

So why is the Iwasaki 6500 and or XM 10k, such a good coral grow bulb? Doens't it lack the blue spectrum and have more of the 500-700 spectrum?
The XM 10k seems to have a good spike at 420, and next to nothing at 450 and beyond.

[ptreef]

ignore

[FlyPenFly]

Depends on the coral, where it was collected, what it's been acclimated to.

I've also noticed some acros love strong flow and polyp extension goes crazy. I've also noticed some acros bleach and die off from too much flow when I moved my pumps around.

I've also noticed some acros color up very pleasingly and grow faster with less light.

No perfect general rules here, just a few guidelines for the most common SPS being grown in tanks.

[sirreal63]

Those lower K bulbs still have plenty of blue in them, it is just doesn't look that way to our eyes because they are overpowered. Keep in mind the violet region is a secondary peak for photosynthesis and those bulbs peak in that area. This is where the PUR comes into play and also where it gets more complicated.

To get a better understanding of what is happening inside the coral...these two articles will help.
http://www.advancedaquarist.com/2011/4/aafeature
http://www.advancedaquarist.com/2012/12/corals

If you make it through those without needing a stiff drink then pat yourself on the back. :D

[Ron Reefman]

@Ron
I see that you understood everything perfectly ;-)

Przemek,
Thank you for your confirmation. I've been reading and talked to several people at MACNA, including Dana Riddle. But I really appreciate your letting me know I got it right. And when I get it wrong, I want you to step in and tell me that as well!

And Jack sites a couple of good articles and makes some good points. And just to be clear PAR is what we can measure with a meter. The Photo synthetically Active Radiation, i.e. all the light between 400nm and 700nm which various organisms use for photosynthesis. PUR (Photo synthetically Usable Radiation) isn't different than PAR, it's a subset of PAR. It's the part of PAR that the coral's zooxanthellae use (mostly blue). And different corals have a different PUR, so we don't have any easy way to measure it.

ptreef asked: So ideally we are looking for a bulb that has the majority of the peaks in the 400-500 spectrum for the corals to color and grow. The rest of the spectrum really is to balance out more so for our visual appeal?

That's pretty much the way it works, yes.

So why is the Iwasaki 6500 and or XM 10k, such a good coral grow bulb? Doens't it lack the blue spectrum and have more of the 500-700 spectrum?
The XM 10k seems to have a good spike at 420, and next to nothing at 450 and beyond.

I don't know the spectrum of that bulb, so I can't say. I'm an old MH user that has moved on to being all led at this point... But I'm considering adding some t5 or BuildMyLEDs long bars of leds for a couple of reasons.

[jda]

Even though we cannot see it, what benefit does true IR and UV on the coral? is it possible that the coral uses that spectrum in part and reflects visible range back out? I have never really seen a good response to this - there might not be any, and that is OK... but I wanted to ask. :)

[sirreal63]

I have no memory of seeing that discussed.