LED Switch moving away from Orphek

Just random info...
Knowledge is power...Love this thread though..very informative and key info for anyone dedicated...

"The problem with PAR is that it measures light within all usable wavelengths, and most photosynthetic organisms aren’t capable of using all of these wavelengths. This means that a PAR reading may not be truly showing how much energy is being emitted that your corals or plants can use. This is where PUR comes in."

Thoughts?

 

Here is something that Sanjay and joshi morgan also wrote:

Realizing that PAR by itself is not a complete measure of the lamp’s usefulness for reef aquaria, a more aggregate view of the spectral distribution and the contribution of the different wavebands to the total PFFD is shown in Figure 3. Figure 3 gives an interesting view of how each lamp performed in six different color bands, each comprising about 50 nm. This view shows how the total PPFD is distributed for each lamp. If we believe that the blue and violet light components of the lamps are more important than the longer wavelengths, then the total significant output in these bands for the 10,000 K, 20,000 K and 6500 K lamps is similar. The output of the 10,000 K Aqualine Buschke lamp is skewed toward the violet end of the spectrum. The output of the 20,000 K Osram/Radium and 10,000 K Coralife are skewed toward the blue end of the spectrum.

Aquarium Frontiers On-Line: Feature

 

There is a difference between no dark spots and shadows and high PAR. 2 will not give consistently high PAR over that area as shown by Sanjay. That may be fine, many people don't need super high PAR. Just depends what you want to keep and where.

PUR is defined for terrestrial plants. Corals are not terrestrial plants. The exact wavelengths which are most useful to corals are dependent on the particular hosted clade of zooxanthellae and the corals pigmentation. This can vary by coral, so, it is not really practical to come up with a general "PUR" for all corals. It may be possible to come up with an optimal wavelength for a specific coral, but the wider range of corals your discussing, such as a typical reef tank, with lots of corals, if we're trying to make all the corals happy, this becomes a pretty big range and PAR becomes better metric although certainly still not completely optimal by any means....

There is certainly some reason to believe certain parts of the 400-700nm range are more beneficial. This range though is not the response curves as defined for terrestrial plants and will vary by corals. Red light is useful for plants, but filtered out very quickly in water. So, pretty much no corals are exposed to red light in nature. Some very shallow water corals and probably clams may be though and may benefit from red. Dana Riddle has shown red to be detrimental to some corals as well though. Red is part of the "PAR" range, but not necessarily desirable. It is also part of the PUR range though. So, this doesn't help. It may help to look at the spectral plots of lights, but there is no defined optimal coral range, so, how useful this is depends on your knowledge of the data and how good the data actually is. It probably is sufficient to say though that for the most part, lights that waste a lot of energy in the yellow-red range, won't be as useful for coral growth as ones with more violet-blue for example.

 

Dont PAR and PUR go kind of hand in hand because they arent separate? PUR is actually the usable radiation in PAR. So PAR is the intensity of the light and PUR would actually be the amount of usable wavelengths within that percentage of intensity?

Im not arguing at all just trying to understand everything better.

 

PAR is not a good measurement with LEDs. The coverage is great with two fixtures running lengthwise and at 12" above water line. Another advantage with AI Sols is they have different lenses available so you can fine tune the lighting to suit your needs.

 

PUR is a range within PAR, useful for terrestrial plants. Corals aren't terrestrial plants... it probably is possible to define some equivalent of PUR for corals, at least specific corals, but this isn't really defined currently. It is used as a marketing gimmick by some companies though.

 

I disagree 99% ;D It is as good of a measure with LEDs as with any other light source.

From Sanjay's article, (Feature Article: LED Lighting Tests: Aquaillumination, Blue Moon, Eco-Lamp KR-91, Ecoxotic Panorama — Advanced Aquarist's Online Magazine) the PAR plot is pretty circular, you don't gain that much by turning lenghtwise. Where the PAR overlaps, of course it will sum, so, from the graph below, if we sum the areas where there would be overlap, we see that you should have over 100 PAR for approx 50" x18" @ 24" from the fixture for example. 100 PAR is fine for some corals, others like more. Just depends what you want to keep.


The PAR from an individual fixture drops off quickly though:

Yes, but the total power doesn't change. You can direct the light better, but the limitation is the wattage. Spreading out light further reduces the light per unit area per time period i.e. PAR.

For example, if you are measuring light 24" from a fixture and have a true 40 degree lens and a true 70degree lens, the coverage areas will be 17.47" and 33.61" respectively. The area of a circle is pi*r*r. So, the 40degree lens at 24" will cover 239.7 square inches, and the 70degree 887.21 square inches. So, the 40 degree lens will have approx 3.7 times the average PAR over the coverage area, but will only cover about 27% of the total area.

 

Where did you happen to find this info at? looking to do some more reading up on it.

 

The 3w LEDs put out so much power I cannot run them at 100% as it is without burning corals so I am happy with my decision and stand by it. All the tests in the world don't compare to the real application.

 

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