ModAquatics
Supporting Member
I have seen many posts asking questions about LEDs, PAR, etc, and instead of answering different post I though I would start one to create more confusion. 
I am not an expert by any means, but I am really into lighting. The information below is based on my personal knowledge.
Here ya go...
The following spectrum's may differ between LED manufacturers. The terminology can apply to different types of lighting but I will concentrate on LED's for now.
LED's come in color and whites (generally speaking).
The colors concentrate on specific wavelength ranges and the LED's are rated by those wavelengths measured in nanometers. (nm=nanometer)
Ultra-violet (UV) 340-420nm Can't see it at the low end, the upper end is violet. It is dangerous at the intensities that we run and should be avoided.
Violet (V) - 410-440nm Burple
Royal Blue (RB) - 440-460nm Very Blue
Blue (B) - 460-490nm Blue
Cyan (C) - 490-520nm Not really used much in aquaria
Green (G) - 520-550nm Good for making green corals pop. Contrary to popular belief, chlorophyll's don't use green very much. Most plants reflect it which is why they appear green. Ideally, if you only give plants or corals the light that they require, they would appear black because they would not reflect any light.
Amber (A) - 570-610nm Not really used much.
Red (R) - 610-645nm Good for making red pop but not used much
Deep Red (DR)- 650-670 Utilized by chlorophyll to produce color. I am experimenting with this and have seen significant color improvement. Especially when combined with Violet LED's. (Thanks SteveB ). Deep Red LED's are very visually powerful and should be used as such.
Anything higher than 670nm gets into infra-red (Heat)
White light covers a broader area of the visible spectrum. Therefore white LED's are typically rated by CRI (color rendition index) or Kelvin (color temperature). Because the white light can cover such a large range we typically call a white LED a general type of white based on where it falls in the Kelvin color temperature range (2000-25,000K for aquarium purposes although it is actually broader). The three white ranges are;
Warm white (WW) - Generally the light has more of the upper warmer part of the spectrum or lower part of the Kelvin color temperature. Typically LED's ranging from 2,500-3,500k fall into this category.
Neutral White (NW) - Middle of the Kelvin range about 3,500-4,500K.
Cool White (CW) - the upper and bluer part of the color temperature 4,500-10,000K
The visible spectrum ranges from approx. 350nm to 750nm. PAR or Photosynthetically Active Radiation is Photon (particles of light) radiation that can be used by plants and animals to produce energy. PAR is light energy between 400-700nm. PAR meters measure an average of light that falls within this range. Because it measures an average, PAR meters cannot accurately measure Color LED's since they are only narrow parts of the PAR range. Even White LED's cannot be accurately measured with a PAR meter because how they are constructed. All white LED's are either Royal Blue or Deep Red LED's with a phosphor coating (that is why the white LED's look yellow when inactive). The phosphor glows white but much of the underlying photon energy comes through. If someone wants to try a cool experiment, hold a white LED under a Royal Blue and watch the white LED light up.
I am not saying that PAR meters are not useful. On the contrary, if a PAR meter says that the LED is putting 100 PAR (It is really call PPFD or Photosynthetic Photon Flux Density but we will just call it 100 PAR until I buy a DeLorean), It is underestimating the true photosynthetic energy hitting the sandbed. This is because different corals and plants utilize different parts of the PAR spectrum differently. Color LED's (Royal Blue specifically) can provide more (here it comes, a new word) PUR or Photosynthetically Usable Radiation. PAR is a general photosynthetic range whereas PUR is the specific parts of PAR that are usable by specific organisms.
Myths......
PAR is PAR - False. There are lights out there that can put out 1000 PAR at the sandbed but some corals would struggle to grow because the light may not have enough PUR for that specific coral. Deepwater corals don't do well under Deep Red light. This is because Deep Red is filtered out after several meters of seawater. Shallow water coral need deep red to thrive better.
The higher the PAR the better - False. There has not been any peer reviewed scientific evidence that I have seen that shows where PAR values higher than 300 have any growth benefit.
There is a specific LED color combination needed - False. White LED's cover a wide spectrum. But some corals grow better under specific color combinations whereas other corals grow better under other combinations. There is none that cover all efficiently. Ask anyone that has run AI's for awhile and they will testify that RB and CW LED's grow a wide range of coral well enough, and other colors are not always necessary.
The best LED efficiency is achieved by running them at higher amperage - False. I see folks doing this all the time and I don't really understand why. Even the LED manufacturers state that the higher the amperage the lower the lifespan and the higher the wasted energy (converted to heat) I suppose people think that the higher amperage produces more light intensity. Although this is true, intensity can be achieved by utilizing optics. The big problem that I have with high amperage is that the LED's produce much more heat per watt and less light per watt.
Again, this information is based on my experience. If anyone has any further info, updates or corrections, let me know and I will change this post as necessary. Please feel free to respond, ask questions, state your experience, etc.
I am not an expert by any means, but I am really into lighting. The information below is based on my personal knowledge.
Here ya go...
The following spectrum's may differ between LED manufacturers. The terminology can apply to different types of lighting but I will concentrate on LED's for now.
LED's come in color and whites (generally speaking).
The colors concentrate on specific wavelength ranges and the LED's are rated by those wavelengths measured in nanometers. (nm=nanometer)
Ultra-violet (UV) 340-420nm Can't see it at the low end, the upper end is violet. It is dangerous at the intensities that we run and should be avoided.
Violet (V) - 410-440nm Burple
Royal Blue (RB) - 440-460nm Very Blue
Blue (B) - 460-490nm Blue
Cyan (C) - 490-520nm Not really used much in aquaria
Green (G) - 520-550nm Good for making green corals pop. Contrary to popular belief, chlorophyll's don't use green very much. Most plants reflect it which is why they appear green. Ideally, if you only give plants or corals the light that they require, they would appear black because they would not reflect any light.
Amber (A) - 570-610nm Not really used much.
Red (R) - 610-645nm Good for making red pop but not used much
Deep Red (DR)- 650-670 Utilized by chlorophyll to produce color. I am experimenting with this and have seen significant color improvement. Especially when combined with Violet LED's. (Thanks SteveB
). Deep Red LED's are very visually powerful and should be used as such.Anything higher than 670nm gets into infra-red (Heat)
White light covers a broader area of the visible spectrum. Therefore white LED's are typically rated by CRI (color rendition index) or Kelvin (color temperature). Because the white light can cover such a large range we typically call a white LED a general type of white based on where it falls in the Kelvin color temperature range (2000-25,000K for aquarium purposes although it is actually broader). The three white ranges are;
Warm white (WW) - Generally the light has more of the upper warmer part of the spectrum or lower part of the Kelvin color temperature. Typically LED's ranging from 2,500-3,500k fall into this category.
Neutral White (NW) - Middle of the Kelvin range about 3,500-4,500K.
Cool White (CW) - the upper and bluer part of the color temperature 4,500-10,000K
The visible spectrum ranges from approx. 350nm to 750nm. PAR or Photosynthetically Active Radiation is Photon (particles of light) radiation that can be used by plants and animals to produce energy. PAR is light energy between 400-700nm. PAR meters measure an average of light that falls within this range. Because it measures an average, PAR meters cannot accurately measure Color LED's since they are only narrow parts of the PAR range. Even White LED's cannot be accurately measured with a PAR meter because how they are constructed. All white LED's are either Royal Blue or Deep Red LED's with a phosphor coating (that is why the white LED's look yellow when inactive). The phosphor glows white but much of the underlying photon energy comes through. If someone wants to try a cool experiment, hold a white LED under a Royal Blue and watch the white LED light up.
I am not saying that PAR meters are not useful. On the contrary, if a PAR meter says that the LED is putting 100 PAR (It is really call PPFD or Photosynthetic Photon Flux Density but we will just call it 100 PAR until I buy a DeLorean), It is underestimating the true photosynthetic energy hitting the sandbed. This is because different corals and plants utilize different parts of the PAR spectrum differently. Color LED's (Royal Blue specifically) can provide more (here it comes, a new word) PUR or Photosynthetically Usable Radiation. PAR is a general photosynthetic range whereas PUR is the specific parts of PAR that are usable by specific organisms.
Myths......
PAR is PAR - False. There are lights out there that can put out 1000 PAR at the sandbed but some corals would struggle to grow because the light may not have enough PUR for that specific coral. Deepwater corals don't do well under Deep Red light. This is because Deep Red is filtered out after several meters of seawater. Shallow water coral need deep red to thrive better.
The higher the PAR the better - False. There has not been any peer reviewed scientific evidence that I have seen that shows where PAR values higher than 300 have any growth benefit.
There is a specific LED color combination needed - False. White LED's cover a wide spectrum. But some corals grow better under specific color combinations whereas other corals grow better under other combinations. There is none that cover all efficiently. Ask anyone that has run AI's for awhile and they will testify that RB and CW LED's grow a wide range of coral well enough, and other colors are not always necessary.
The best LED efficiency is achieved by running them at higher amperage - False. I see folks doing this all the time and I don't really understand why. Even the LED manufacturers state that the higher the amperage the lower the lifespan and the higher the wasted energy (converted to heat) I suppose people think that the higher amperage produces more light intensity. Although this is true, intensity can be achieved by utilizing optics. The big problem that I have with high amperage is that the LED's produce much more heat per watt and less light per watt.
Again, this information is based on my experience. If anyone has any further info, updates or corrections, let me know and I will change this post as necessary. Please feel free to respond, ask questions, state your experience, etc.
