growing corals with only actinics?

[renisel]

Has anybody ever tried growing corals using only actinic lighting? Chlorophyll gets its best absorption around 450 nm, which is roughly where actinics put out most of their light. This would suggest to me that not only should it be possible to meet all of the corals' photosynthetic needs with actinic lighting, but that might also be considerably more efficient than a broad-spectrum light that imitates sunlight. So, in situations where you are almost exclusively concerned with coral growth--such as in a frag tank--it might be best to use actinics as the sole or primary light source. I'm thinking about giving this a try on my frag tank, but thought I'd first check to see if anybody else has tried something similar, or knows of a reason why it shouldn't work.

 

[sterling18]

Interesting, might work. The coral that are found in high K should.

 

[sterling18]

Thoughts anyone?

 

[tmz]

I don't think actinic provides enough PAR(photosynthetically availabe radiation) to sustain or grow corals.

 

[pdelcast]

I don't think there would be any problem with using actinic only lighting -- it would simulate lighting very deep in the reef, and the corals would probably love it.

But our eyes aren't very sensitive to 420nm, so your tank will look very blue and dark.

 

[renisel]

<a href=showthread.php?s=&postid=13211751#post13211751 target=_blank>Originally posted</a> by tmz
I don't think actinic provides enough PAR(photosynthetically availabe radiation) to sustain or grow corals.

Yes, actinics provide low PAR readings, but I think this can be misleading. To the best of my understanding, PAR is a measurement of the total light provided in the range where photosynthesis occurs, regardless of how well the light at each wavelength is actually utilized by photosynthetic organisms. Both chlorophyll and carotenoids have wide bands in that spectrum where they absorb virtually no energy from the light whatsoever.

The range where the light is most effectively absorbed by the photosynthetic pigments is around 420-500 nm, which is where actinics focus their energy. So, while they may provide less PAR, due to the fact that their radiation is more effectively utilized, they may actually provide more photosynthetic energy to the organism per watt of energy pushed into the lamp.

 

[renisel]

<a href=showthread.php?s=&postid=13211879#post13211879 target=_blank>Originally posted</a> by pdelcast
I don't think there would be any problem with using actinic only lighting -- it would simulate lighting very deep in the reef, and the corals would probably love it.

But our eyes aren't very sensitive to 420nm, so your tank will look very blue and dark.

That's pretty much what I was thinking. I haven't been diving in a few years, but from what I remember, there are still plenty of corals growing down in the deeper waters where the light is filtered to the point that red objects appear more-or-less black. I agree that it probably wouldn't be the greatest lighting scheme for a display tank, but as I said, it might be a good way to light a frag tank.

 

[JCTewks]

renisel: PAR is measured as the total Photosynthetically Available Radiation (PAR ) so; while blue has more energy per unit than red, PAR is reading total energy not total units. Therefore wether the light be pure red or pure blue it's the same amount of AVAILABLE photons if the PAR reading is the same. ie. if a "red" light has a PAR of 100 and a "blue" light has a PAR of 100 they will both grow the coral at the same rate. If you have 2 bulbs of similiar PAR that are different "colors" the coloring (pigmenting cells) of the coral will be affected, while the growth will be equal.

 

[JCTewks]

While the PAR of actinics IS lower than a full spectrum bulbs, I would think that if you use enough bulbs to provide adequate PAR for the corals that the colors would be pretty amazing!!!

"blue" bulbs tend to color up corals better than "yellow" bulbs.

 

[renisel]

<a href=showthread.php?s=&postid=13215181#post13215181 target=_blank>Originally posted</a> by JCTewks
renisel: PAR is measured as the total Photosynthetically Available Radiation (PAR ) so; while blue has more energy per unit than red, PAR is reading total energy not total units. Therefore wether the light be pure red or pure blue it's the same amount of AVAILABLE photons if the PAR reading is the same. ie. if a "red" light has a PAR of 100 and a "blue" light has a PAR of 100 they will both grow the coral at the same rate. If you have 2 bulbs of similiar PAR that are different "colors" the coloring (pigmenting cells) of the coral will be affected, while the growth will be equal.

Is the PAR scale adjusted for the degree to which the photosynthetic pigments absorb the various wavelengths? To the best of my knowledge, it isn't, which is why it can be misleading. Yes, all of the radiation between about 400 and 700 nm is technically available for photosynthesis; but different wavelengths are utilized to different extents.

A relatively large portion of the light in the 400-500 nm range that hits a photosynthetic cell will be absorbed, while only a very small portion of the light in the 600 nm range will be absorbed and converted to usable energy. However, the PAR reading would recognize 100W of 420 nm light as being equivalent to 100W of 600 nm light. Meanwhile, that 100W of 420 nm light might translate into 80W of photosynthetically-produced power available to the organism, while the 100W of 600 nm light might translate into only 10W of power available to the organism. Since what we're concerned with is the energy provided to the corals in the end, the PAR measurement misleads us when it says that 100W of 420 nm light is equal to 100 W of 600 nm light.

 

[tmz]

<a href=showthread.php?s=&postid=13215191#post13215191 target=_blank>Originally posted</a> by JCTewks
While the PAR of actinics IS lower than a full spectrum bulbs, I would think that if you use enough bulbs to provide adequate PAR for the corals that the colors would be pretty amazing!!!

"blue" bulbs tend to color up corals better than "yellow" bulbs.

No doubt about the color. My favorite tank is a 90 g lps with 220 actinic and20k l75 w mh. Thanks for clarifying the PAR issue. It's about the way I see it.

 

[SALT WATER CRAZ]

It would be intresting to see a tank set up with actinics only.

 

[JCTewks]

<a href=showthread.php?s=&postid=13215387#post13215387 target=_blank>Originally posted</a> by renisel
Is the PAR scale adjusted for the degree to which the photosynthetic pigments absorb the various wavelengths? To the best of my knowledge, it isn't, which is why it can be misleading. Yes, all of the radiation between about 400 and 700 nm is technically available for photosynthesis; but different wavelengths are utilized to different extents.

A relatively large portion of the light in the 400-500 nm range that hits a photosynthetic cell will be absorbed, while only a very small portion of the light in the 600 nm range will be absorbed and converted to usable energy. However, the PAR reading would recognize 100W of 420 nm light as being equivalent to 100W of 600 nm light. Meanwhile, that 100W of 420 nm light might translate into 80W of photosynthetically-produced power available to the organism, while the 100W of 600 nm light might translate into only 10W of power available to the organism. Since what we're concerned with is the energy provided to the corals in the end, the PAR measurement misleads us when it says that 100W of 420 nm light is equal to 100 W of 600 nm light.

AFAIK, the PAR scale is "weighted" for photosynthesis...now I'm not sure how accurately it is weighted. But, even if it were accurately weight for ChA, it would be different for ChB, as well as all of the other compounds photosynthesizing.

The ONLY reason that the 100w 600nm bulb would have more available radiation than the 100w 420nm bulb is that it is easier for a bulb to produce the higher wavelengths...hence why a 20K MH will have less PAR than a 10K. The PAR difference has niothing to do with spectrum, only how effectively a bulb can produce blue.

but really, your comparison using watts is fairly useless as we are discussing PAR itself, not watts of power/PAR ratios. If you look at PAR and spectrum ONLY, you will find that PAR is PAR is PAR across the spectral range from 420nm-710nm. Like I said earlier, PAR (remember, the P is for photosynthetic ) is geared toward the spectral curve that photosynthesis occurs (in a broad sense, covering many photosynthetic compounds).

 

[renisel]

<a href=showthread.php?s=&postid=13215522#post13215522 target=_blank>Originally posted</a> by JCTewks
AFAIK, the PAR scale is "weighted" for photosynthesis...now I'm not sure how accurately it is weighted. But, even if it were accurately weight for ChA, it would be different for ChB, as well as all of the other compounds photosynthesizing.

The ONLY reason that the 100w 600nm bulb would have more available radiation than the 100w 420nm bulb is that it is easier for a bulb to produce the higher wavelengths...hence why a 20K MH will have less PAR than a 10K. The PAR difference has niothing to do with spectrum, only how effectively a bulb can produce blue.

but really, your comparison using watts is fairly useless as we are discussing PAR itself, not watts of power/PAR ratios. If you look at PAR and spectrum ONLY, you will find that PAR is PAR is PAR across the spectral range from 420nm-710nm. Like I said earlier, PAR (remember, the P is for photosynthetic ) is geared toward the spectral curve that photosynthesis occurs (in a broad sense, covering many photosynthetic compounds).

Well it looks like a significant part of our disagreement hinges upon whether the PAR measurement is or is not weighted (and even if it is, there could be a debate over how relevant the weighting function is to the photosynthetic processes carried out in corals, as I would bet it would be geared primarily toward plants). I had been under the impression that it was unweighted; however, after a bit more reading, I believe that was incorrect. I found a few sources that said it is measured in terms of luminous flux--which would mean that it is weighted to reflect the brightness as perceived by humans. I find this somewhat difficult to believe, as it would appear to me that such a scale would be almost the inverse of the absorption spectra for photosynthetic pigments. If you can find a resource that shows the weighting function for PAR measurements, I'd be pretty interested to see it.

I'm not entirely sure what you're getting at in the second paragraph. How is it easier to produce the longer wavelengths? You mean they are lower energy, so there will be more 600 nm photons emitted per unit energy than 420 nm photons? And if the PAR value has nothing to do with spectrum, how is it contingent upon the effectiveness of production of blue light (a specific segment of the spectrum)?

Actually, I think my discussion of power was quite apt because, as I said, we are really concerned with power produced by the algae per unit power put into the lighting system (or at least I am, as this would imply the most efficient way to grow corals).

 

[SasquatchFarmer]

<a href=showthread.php?s=&postid=13215829#post13215829 target=_blank>Originally posted</a> by renisel
Well it looks like a significant part of our disagreement hinges upon whether the PAR measurement is or is not weighted (and even if it is, there could be a debate over how relevant the weighting function is to the photosynthetic processes carried out in corals, as I would bet it would be geared primarily toward plants). I had been under the impression that it was unweighted; however, after a bit more reading, I believe that was incorrect. I found a few sources that said it is measured in terms of luminous flux--which would mean that it is weighted to reflect the brightness as perceived by humans. I find this somewhat difficult to believe, as it would appear to me that such a scale would be almost the inverse of the absorption spectra for photosynthetic pigments. If you can find a resource that shows the weighting function for PAR measurements, I'd be pretty interested to see it.

I'm not entirely sure what you're getting at in the second paragraph. How is it easier to produce the longer wavelengths? You mean they are lower energy, so there will be more 600 nm photons emitted per unit energy than 420 nm photons? And if the PAR value has nothing to do with spectrum, how is it contingent upon the effectiveness of production of blue light (a specific segment of the spectrum)?

Actually, I think my discussion of power was quite apt because, as I said, we are really concerned with power produced by the algae per unit power put into the lighting system (or at least I am, as this would imply the most efficient way to grow corals).

Great! It seems as though a more "accurate" unit of measure would be desirable for corals. I would assume that many plants are exposed to basically the same spectrum of light, where as corals may be subjected to a vastly different spectrum of light (depending upon what depth they naturally occur) that is skewed towards the blue. Wouldn't it be more accurate to develop a differently unit of measure that is more specific for certain coral species or depth zones?

 

[madadi]

in my tank i use T5HO actinic and T12VHO actinic. combined they make an awesome light. if you do this, i would recommend you go with a mixture of ATI blue+ giesemann actinic+ T5s and URI actinic VHOs. VHOs peak at 420 while the bluer T5s peak at 450nm.

 

[JCTewks]

renisel: I started a new thread to coninue this disussion in the hopes that others with more knowledge would chime in.

http://reefcentral.com/forums/showthread.php?s=&threadid=1458071

I was looking for the articles that I've read in the past about PAR and can't seem to find any of them.

I do know that PAR is not weighted the same as lux (which is weighted for how the human eye percieves light).


While I agree that there is merit to PAR:watt ratios, I believe it will only cause confusion within the current discussion of "what is PAR and how is it weighted". It can be noted that almost ALL bulbs will put out more PAR when their output is in the lower K rankes, while the high K bulbs PAR is significantly less...hopefully that can be cleared up in the other thread.

SasquatchFarmer: At this point PAR is the most "accurate", and readily available measure for how much light corals need/can use...it is a much better suited test than Lux or Lumens!

 

[adamsaranluke]

more knowledge?

more knowledge?

<a href=showthread.php?s=&postid=13221247#post13221247 target=_blank>Originally posted</a> by JCTewks
renisel: I started a new thread to coninue this disussion in the hopes that others with more knowledge would chime in.

You were hoping someone with more knowledge would chime in? I think between the two of you, you possess most or all of the available knowledge on this subject already. Good luck finding someone smarter!

 

[JCTewks]

LOL, I can't speak for renisel, but I for one can sure learn a lot more :lol::lol:

 

[second_decimal]

i have always been under the impression that actinics, while they do assist in coloration, actually have very little impact on the actual growth. Are you both implying that the general consenus is flawed?