# Lighting Demystified



## Gizmo (Dec 6, 2010)

Alright, so here's my take on the lighting systems out there right now. Correct me if I am wrong:

Example: 24 Watt 10,000 K 420-480 nm Actinic T5HO Light Bulb

P = VI: 24 Watts means 24 Volt-Amperes, a ratio of the voltage vs. current. Usually, lights have low current and high voltage. So a 0.5 Amp light with a 24 Watt rating pulls 48 Volts. The higher the Wattage, the more powerful the light.

10,000 K = temperature rating, in degrees Kelvin (absolute). Degrees Farenheit = [(Degrees Kelvin + 273.15)*(9/5)]+32. Generally is just an indicator of the light spectrum your bulb will be putting out.

420-480 nm - Wavelength. Indicates the type of electromagnetic radiation by the length of a full cycle of the wave. Visible light occupies the spectrum from 390-750 nm, with red at the low end, violet at the high end (hence infrared (below red) and ultraviolet (above violet). Frequency = speed of light/wavelength (F = c/lambda, in Hertz or cycles/second). Higher frequencies (shorter wavelengths) attenuate faster (get weaker), so longer wavelengths (near violet, blue, UV, etc.) are better for penetrating a deep tank to reach the bottom.

Actinic - Flashy name for UV light. Usually blue in color, good for reef tanks (not sure why).

The true measure of light is using measurements known as PAR measurements - Photosynthetic Active Radiation, expressed in micro-mol per meter squared per second (umol/m^2/s). PAR meters are expensive! Generally, Watts per Gallon (WPG) is the conventional measure used for tanks, but that is dependent on depth of tank and wavelength of light.

Note: Bulbs DO wear out, so be wary!

Hope this helps! And if anyone has anything to add and/or correct, let me know!


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## beaslbob (May 29, 2009)

[email protected] said:


> .
> 
> ...
> 
> ...


this is incorrect. Actinic lights are different from UV lights. The UV or black lights were tested by one poster on another board and did not light things up very well and plastic egg crates in the tank became week and brittle to the point of falling apart in the poster's hands. they also can create problems with retina damage to eyes.

My concern here is that some wise reef tank owner would go out and try a UV light instead of actinic. Which is not recommended and is actually dangerous.

Actinics are good for reef tank to light activate corals, show off good coloration because they simulate the light wave length at deapths of 30' or more where the red part of the sun's rays have been filtered out by the water column.


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## Gizmo (Dec 6, 2010)

Thanks for setting me straight beasel


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## beaslbob (May 29, 2009)

[email protected] said:


> Thanks for setting me straight beasel


hopefully I was correct. *old dude

Actually it is very common as from what I hear the wave lenghs of UV and actinic are pretty close.

Now I think I hear the experts comming. *w3


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## mfgann (Oct 21, 2010)

[email protected] said:


> ...The higher the Wattage, the more powerful the light.


Just to clarify, the higher the wattage the more power is being used. The reason I need to clarify is that Incandescent lights rated at 20W is not putting out as much light as a T12 florescent rated at 20W. Much of the power is wasted in heat. Similarly, a T8 is even more efficient, and a T5 more than that. I've seen the 2W/gallon florescent rule modified down to about 1.5W/gallon for a T5. Next on the list is LED lights, which make the florescent lights look like energy hogs. When the price on these drops and there is a little more experience on about how much LED light is needed per gallon, they will be a very good choice. A watts/gallon rule is misleading, but the best poor-mans measurement we have, until PAR meters are $10 at walmart.


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## Gizmo (Dec 6, 2010)

From what I've read, Power Compact is the least powerful, T5HO is the next best, MH is the next, and LED's are the top of the line. Price is proportional to quality. I've heard 130W PC ~ 72W T5HO ~ 60W MH ~ ?? LED. I'm currently running a 48W 20" T5HO set with a full spectrum and a 10k daylight bulb. Plant growth is decent, but until now I thought a 130W PC light would be better...not!


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## beaslbob (May 29, 2009)

for the watts per gallon to be at all close it must be watts of normal output flourescent lights. In the case of the spiral incadescent replacement bulbs that is the actual wattage not the equilivant as stated above.


my .02


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## Gizmo (Dec 6, 2010)

A note on temperature ratings -

The higher the temperature rating, the brighter the light. The lower the temperature rating, the better plants like it. i.e. 1600K daylights are not as good for plants as 1000K, and 10,000K are bright as all getout.


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## beaslbob (May 29, 2009)

[email protected] said:


> A note on temperature ratings -
> 
> The higher the temperature rating, the brighter the light. The lower the temperature rating, the better plants like it. i.e. 1600K daylights are not as good for plants as 1000K, and 10,000K are bright as all getout.


not necessarily true although some 10000k actinics are extremely bright because they are 250w bulbs.

The K refers to the temperature a "black body radiator" would be heated up to. And at the temperature the light spectrum emitted. the higher the K the bluer the light. but the lumes or par generated could be higher or lower then other k values depending on the power used and so on.

my .02

reference:

Color temperature Definition from PC Magazine Encyclopedia

(dern I was correct. *old dude)


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## aalina387 (Feb 14, 2011)

*The Beauty of an Indoor Garden Using Grow Lights*

I think you should try LED lights they produce less heat and also energy efficient.These lights are inexpensive and quite effective.


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## Gizmo (Dec 6, 2010)

*Re: The Beauty of an Indoor Garden Using Grow Lights*



aalina387 said:


> I think you should try LED lights they produce less heat and also energy efficient.These lights are inexpensive and quite effective.


I agree, however, research on the actual quality of LED lights is still marginal.


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## susankat (Nov 15, 2008)

If you all would collaborate on a good draft of this, we can sticky the post.


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## Gizmo (Dec 6, 2010)

susankat said:


> If you all would collaborate on a good draft of this, we can sticky the post.


I'll work on it. If anybody wants to add anything, posts would be appreciated in this thread.


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## aalina387 (Feb 14, 2011)

The LED lights require a very low voltage and therefore consume much less electricity than a normal light and they stay relatively cool.


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## Gizmo (Dec 6, 2010)

Apparently, the posts won't let me post everything I wanted to type. I'll work on trimming it.


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## M1ster Stanl3y (Dec 10, 2010)

[email protected] said:


> Alright, so here's my take on the lighting systems out there right now. Correct me if I am wrong:
> Example: 24 Watt 10,000 K 420-480 nm Actinic T5HO Light Bulb
> P = VI: 24 Watts means 24 Volt-Amperes, a ratio of the voltage vs. current. Usually, lights have low current and high voltage. So a 0.5 Amp light with a 24 Watt rating pulls 48 Volts. Generally the higher the Wattage, the more powerful the light.
> 10,000 K = black-body temperature rating, in degrees Kelvin (absolute). Degrees Farenheit = [(Degrees Kelvin + 273.15)*(9/5)]+32. Degrees Celsius = Degrees Kelvin + 273.15. Generally is just an indicator of the light spectrum your bulb will be putting out, can also apply to intensity.
> ...


AHHH MATH!!!!! RUN FOR THE HILLS!!! JK JK, haven't taken a math class in 11 yrs and im only 27. so AHHHHH....I might hafta do an LED experiment on my 10g to see what i need to make my plants grow like they do with the current lighting.


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## Gizmo (Dec 6, 2010)

M1ster Stanl3y said:


> AHHH MATH!!!!! RUN FOR THE HILLS!!! JK JK, haven't taken a math class in 11 yrs and im only 27. so AHHHHH....I might hafta do an LED experiment on my 10g to see what i need to make my plants grow like they do with the current lighting.


If you need to borrow my light meter, I'll ship it to you, just be a nice moral individual and return it to me plz


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## M1ster Stanl3y (Dec 10, 2010)

I would say sure but: 
A) arent they expensive?
B) Arent they expensive?
C) I have a 5yr old who steals my tools..


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## Gizmo (Dec 6, 2010)

M1ster Stanl3y said:


> I would say sure but:
> A) arent they expensive?
> B) Arent they expensive?
> C) I have a 5yr old who steals my tools..


A and B - I bought a discontinued Milwaukee SM700 Lux meter for $50 still in the packaging, found manuals and Lux to PAR algorithms and conversion constants online. So for $50 I got a $100 piece of equipment. Still has the plastic guard on the readout screen 

C - As long as your child doesn't break it, I'm alright with that. If he/she does, it's $50.


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## M1ster Stanl3y (Dec 10, 2010)

once i get it all set up ill let ya know. i know lowes sells a 3 led bar for under cabinets for like 9-19 dollars i forget how much. im thinking maybe 2-3 of these if they are the $9 price. at $19 ill find a different one to try out.


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## jrman83 (Jul 9, 2010)

Personally, if this was for someone new, although I know you say avg aquarists, it's too technical. If this is what I was supposed to read to get me looking at the light I need I would probably get done and ask someone to tell me what I needed anyway. Good info, just a little too technical, IMO. Information overload sort of. Just tell the stuff I _need_ to know and I'm happier. I like it personally, but the avg new guy/gal would skim over all the technical stuff.


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## Gizmo (Dec 6, 2010)

jrman83 said:


> Personally, if this was for someone new, although I know you say avg aquarists, it's too technical.


I removed some of the math. Better now?


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## jrman83 (Jul 9, 2010)

That is much better. Easier to follow.


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## beaslbob (May 29, 2009)

gee I can make this more complex*old dude

power is defined in watts which under purely resistive loads is volts times amps. The first thing that "screws" that up is the power consumed by the entire fixture is always more then the power used by the tubes themselves. Power is lost in the ballasts. Plus (ELI the ICE man {memory trick LOL}) volts (E) lead current (I) in inductors (L) and current leads volts in capacitors. All of this combines to form a power factor where the actual power being delivered to the lights is lower then the power consumed by the fixture. So a power factor of say .9 means that only .9*times the fixture wattage is actually delivered to the bulbs.

The general rules of thumb 1,2,3 watts per gallon are subjective and not hard and fast. But even more importantly apply to planted Freshwater tanks (usually planted) only. Coral reef marine tank have much higher watts per gallon recomendations.

Kelvin ratings are defined as stated but reflect only the frequency spectrum not the intensity or anything else. The higher Kelvin ratings are bluer and reflect frequncy spectrums at deeper water levels. Below 30' or so you see the nice pretty blue colors on all those ocean movies. Hence the higher kelvin ratings simulate that color spectrum.

The T sizes for flourescent tubes is actually the diameter of the tube in 1/8" steps. t5 is 5/8", t8 is 8/8 (1"), t12 is 12/8. etc etc.

PAR is used by plants but there is actually no accepted scientific standard definition. 

Lux is the lumens per unit area. Lumens is related to foot candle. All of which is related to how the human eye see things. So each power(intensity) of each wave length is weighted to reflect the response of the eye. If humans cannot see that wave lenght it has no weight.

Of course plants may respond differently then the human eye so Lux not be useful to our aquariums. (unless we want to see the fish. *old dude)

The reflector is important. 

If you have a point souce (incandescent bulb) the light travels outward in a sphere around the source. As the distance from the source increases the light is dispersed over the area of the sphere. Therefore, doubling the distance results in the light covering 4 times the area. Tripling the 9 times and so on. The light decreases by 1/distance squared.

If the light is coming from a line source (kinda like a long tube) the light travels in a cylinder around the tube. So as the distance doubles the circumference of the light halves. Triples 1/3 etc etc etc. So the light decreases by 1/distance.

If the light comes from an area source with all waves parallel then the light does not decrease the further you get away from the source.

In the real world we don't have actual point, line, or area sources. When you are very close to a point source is can appear to be a line or area source. Our tubes have a finite length and so on. But those general concepts are valid to explain things and make engineering decisions. For instance, assuming point sources for gravity is more the adequate at plantary distances. But assuming a point source for the 4' long light tube 3" above the water line on our aquariums would not be.

So reflectors attempt with varying effeciencies to reflect the light so that it is an area souce. And by doing that can reduce the wattage (expense) used to light the tank at some level.


All of which is an old man remembering an old physics course and some technical/engineering courses. So therefore subject to correction.

Worth not more then .02 *old dude

But I like the discussion. *w3


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## Gizmo (Dec 6, 2010)

beaslbob said:


> The first thing that "screws" that up is the power consumed by the entire fixture is always more then the power used by the tubes themselves. Power is lost in the ballasts. Plus (ELI the ICE man {memory trick LOL}) volts (E) lead current (I) in inductors (L) and current leads volts in capacitors. All of this combines to form a power factor where the actual power being delivered to the lights is lower then the power consumed by the fixture. So a power factor of say .9 means that only .9*times the fixture wattage is actually delivered to the bulbs.
> 
> Coral reef marine tank have much higher watts per gallon recomendations.
> 
> Kelvin ratings are defined as stated but reflect only the frequency spectrum not the intensity or anything else. The higher Kelvin ratings are bluer and reflect frequncy spectrums at deeper water levels.


Thanks for all the info beaslbob! Definitely putting me to shame (I'm still a college student). I'm editing my post to try and reflect some of what you added. Questions:

Am I getting my attenuations mixed up? I thought lower wavelengths (blue light) attenuated faster. Low wavelengths = high frequency (lambda = c/f), and I know for a fact that UHF and VHF radios are line-of-sight, while the Navy uses VLF and ULF radio to communicate with submarines underwater.


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## susankat (Nov 15, 2008)

I don't like the worse than this one and that one is worse than that one.


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## Gizmo (Dec 6, 2010)

susankat said:


> I don't like the worse than this one and that one is worse than that one.


Edited, let me know if it looks better.


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## beaslbob (May 29, 2009)

[email protected] said:


> Thanks for all the info beaslbob! Definitely putting me to shame (I'm still a college student). I'm editing my post to try and reflect some of what you added. Questions:
> 
> Am I getting my attenuations mixed up? I thought lower wavelengths (blue light) attenuated faster. Low wavelengths = high frequency (lambda = c/f), and I know for a fact that UHF and VHF radios are line-of-sight, while the Navy uses VLF and ULF radio to communicate with submarines underwater.


I think the real bottom line is we need to get lights that 1) make the tank look nice, and 2) feed to plant life..

I get my wave lengths and frequencies mixed up as will. the higher frequency shorter wave lengths do attenuate faster. Just as AM radio travels further the FW. And it uses the ground as well. 

But you are correct the blue light is shorter wave lenght, high frequencies and therefore should attunate quicker. In our aquarium that does make sense as to why we have to have such high powered actinic bulbs in our reef tank. But in my humble confused mind should also mean that the blue lights is attunuated faster in the ocean. so perhaps someone can help me out. Perhaps it is just the ocean filtering at work not the attenuation.

We also had survivable low frequency system in the south dakota missile fields. They use buried huge antennas and the resultant long wave length signals traveled through the ground. 

So I guess I got myself confused somehow.

my .02


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## Gizmo (Dec 6, 2010)

beaslbob said:


> But in my humble confused mind should also mean that the blue lights is attenuated faster in the ocean.


Perhaps the higher wavelength (lower frequency) light that is penetrating the ocean at depth is hitting water molecules and being re-emitted at a different wavelength? Maybe it's the same reason the atmosphere is blue during the day.

As the sun sets, it turns red because the atmosphere filters out everything but the red wavelengths. HOWEVER, directly over the surface of the water at sea, the last little bit of the sun as it dips below the horizon flashes green. I've seen it, and know it's called the Green Flash. Interesting phenomenon...


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## jrman83 (Jul 9, 2010)

[email protected] said:


> ....below the horizon flashes green. I've seen it, and know it's called the Green Flash. Interesting phenomenon...


Yes, pretty cool. Being in the surface Navy, I have seen it many times. Considered a natural phenomenon. I remember one night we had 3 (natural phenom.) in one night...a moonbow (yes, they exist), a comet (hailbop or whatever that one was about 10yrs ago, and of course the green flash. Cool stuff.

We do use UHF mostly (satellite however), with a little VHF thrown in. However, SHF is becoming the most widely used and moving into Ku band - both satellite comms.


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## M1ster Stanl3y (Dec 10, 2010)

Walmart sells a $10 24inch single bulb fixture. It says its for plant growth and comes with a 17watt bulb, but it says it putts out 75watts. How can it up the light by, what, 5x?


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## jrman83 (Jul 9, 2010)

M1ster Stanl3y said:


> Walmart sells a $10 24inch single bulb fixture. It says its for plant growth and comes with a 17watt bulb, but it says it putts out 75watts. How can it up the light by, what, 5x?


Don't see how they get that kind of wattage, unless they are referring to the similar output. Same way CFL bulbs in Lowe's say 26W, but they are 100W equivalent, referring to incadescent bulbs which most of us grew up using.

Even a 24" T5HO will not be 75w.


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## Gizmo (Dec 6, 2010)

M1ster Stanl3y said:


> Walmart sells a $10 24inch single bulb fixture. It says its for plant growth and comes with a 17watt bulb, but it says it putts out 75watts. How can it up the light by, what, 5x?


They could mean a fixture that draws 75 Watts out of the wall outlet to drive a 17 Watt bulb. If so, that has to be one of the most horrible fixtures I've ever heard of.


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## Gizmo (Dec 6, 2010)

jrman83 said:


> We do use UHF mostly (satellite however), with a little VHF thrown in. However, SHF is becoming the most widely used and moving into Ku band - both satellite comms.


So let me try and puzzle this out, follow my logic, and correct me if I am wrong, because I seem to be quite misconstrued:

Undersea communications utilize ULF, however, satellite comms utilize UHF - what in the world? You would think that a 40,000kilometer distance through some crazy stuff like the Earth's ionosphere would cause some horrendous attenuation, unless the ionosphere instead of attenuating a signal just adds noise and interference. I know for a fact that low frequencies travel though lossy media better and loss=attenuation, however up until now I thought that interference and noise also generated attenuation. Am I wrong?

I also know you can deliver much more intense radiation at high frequencies (a measure of how much energy is being transmitted), which is indicative of the higher power requirements to generate such high frequencies.


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## jrman83 (Jul 9, 2010)

I dunno...LEO satellites I guess.


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## M1ster Stanl3y (Dec 10, 2010)

[email protected] said:


> They could mean a fixture that draws 75 Watts out of the wall outlet to drive a 17 Watt bulb. If so, that has to be one of the most horrible fixtures I've ever heard of.


right on top of the packaging it says 75watt light output uses 17 watts of energy. The bulb is a 17w RB17T8. its r ated at 7800k. Maybe its magic??? :-o


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## susankat (Nov 15, 2008)

Try going off this;

courtesy of David Stewert
Member of the OKAA

Aquarium Lighting: 
How is light measured?

The Visible Spectrum of Light



•Visible light is on a scale in nanometers from 400nm (violet) to 700nm (red).
The blue and red zones of the visible spectrum are the most beneficial to plants and algae.
Green plants appear green because they reflect the green part of the spectrum. 
The human eye is most sensitive (brightest) in the green spectrum (middle of visible spectrum, or around 550nm).

CRI: Color Rendering Index

•CRI is a measurement of how accurately a light source can produce colors in objects.
Scale is from 0 to 100 Natural Sunlight is 100.
The higher the number the more vibrant the colors will appear.
Have you ever bought a piece of clothing in a store only later to realize that in natural sunlight the color looks different, most likely the store was using low CRI Bulbs.
CRI has very little meaning to aquarium occupants as it is based on human vision.

Lumen


The light that the human eye can see VS. The light that aquarium photosynthetic animals like

•The lumen is a measure of flux, or how much light energy a light source emits (per unit time). 
The lumen measure does not include all the energy the light emits, just the human visible wavelengths.
The lumen has very little meaning to aquarium occupants as it is based on human vision.
Lux = Lumens/Square Meter

Watts

•Watt is a unit of electrical consumption, not of light energy.
The amount on energy that your lighting system consumes may have little to due with how much usable light is emitted.
The watts/gallon rule as applied to aquariums continues to be outdated as more efficient lighting source are able to squeeze more usable light from each watt.
This measurement can give you an idea how much light is produced if comparing apples to apples.

Kelvin

•The Kelvin rating is a indication color temperature.
The Kelvin rating for light sources:
– 2,700K- average incandescent light bulb
– 5,500K – Daylight
– 10,000K – Blue Sky
It is the average of all the light emitted from the light source.
Two identical Kelvin rated light sources can be composed of vastly different wavelengths of light.
This measurement can give you a general idea of the color and composition of the light.
Personally I think some of the numbers stamped on the bulbs are just for marketing.

PAR

•PAR - Photosynthetic Active Radiation or Photosynthetic Available Radiation
PAR accounts with equal weight for all the output a light source emits in the wavelength range between 400 and 700 nm.
PAR differs from the lumen in the fact that it is not a direct measure of light energy, but rather light energy that is useable for photosynthesis.
It is expressed in "number of photons per second".
The reason for expressing PAR in number of photons instead of energy units is that the photosynthesis reaction takes place when a photon is absorbed by the plant.
PAR is one of the most meaningful measurements to aquarium occupants (PAR figures are not listed on lighting systems, as they are setup specific).

Application to Aquariums

Fish only Tanks

•From a color temperature standpoint (Kelvin rating): 
Blue-colored light (10,000K) will enhance blues in your fish. 
Green-colored light (5,500K – 6,700K) will make the tank look bright to humans and enhance the green color of your plants. 
Red-colored light (2,700K) will enhance the reds in your fish, and any red plants.
The light cycle can be important to trigger spawning (or a change in the light cycle).
The amount of light can be used to control algae.

Planted Freshwater/Marine



•For green plants the lighting peaks that are most important:
– Chlorophyll-a: 430nm/662nm
– Chlorophyll-b: 453nm/642nm
– Carotenoids: 449nm/475nm
– Blue Green Algae (cyanobacteria), which contain Phycocyanin and absorb light heavily in the low 600nm (orange-red).
Red pigmented plants use more light in the blue area (450nm) of the spectrum.
If your lighting looks extremely bright and your plants seem ultra-green, it means that you have lighting that outputs strongly in the green spectrum.

Marine Reef

•When light penetrates the ocean, the red spectrum is filtered out. (This is why the ocean appears blue).
Sunlight at the waters surface has a color temperature of 6,500K.
The light spectrum approximate a depth of 5 to 10m (16.5 to 33 feet) is 10,000K.
The spectrum is equivalent of light at a depth of about 20m (66') is 20,000K.
Most standard lighting is in the 6,700K range in order to get a (Higher Kelvin) rating Actinic (lighting that ranges from ~380 nm to ~480 nm, with a major peak at ~420 nm) bulbs are often used as a supplement.
Zooxanthellae(Zoo-zan-THEL-lee) are symbiotic Algae located inside various marine invertebrates (Corals, Anemones, and Clams) they can provide up to 90% of a coral’s energy requirements.
Zooxanthellae utilize Chlorophyll-a and Chlorophyll-c
The absorbance spectra for Zooxanthellae is much broader in the Blue spectrum (400 - 450nm).

Lighting Types

Natural Sunlight

•Great Light & Free
Impossible to Control

Incandescent

•The hardware is very cheap.
Most energy is wasted as heat only 17 Lumens per watt.
Incandescent has very poor quality of light typically 2,700K.
Compact Florescent is the spiral bulb now used to replace incandescent bulbs. 
Uses less electricity
Ballast is not remote 
Very high restrike

Fluorescent

•T designation is based on 1/8th of an inch 
– T12 = 1.5 inches
– T8 = 1 inch 
– T5 = .625 inches
NO - Normal Output
HO – High Output
VHO – Very High Output

Normal Output Fluorescent

•NO is in a standard aquarium hood that is included in most aquarium combo setups.
It is also what is used in shop lights and most home installations.
T12 has a output of approx 55-75 Lumens per watt (magnetic or electronic ballast).
T8 has a output of approx 80-90 Lumens per watt (magnetic or electronic ballast).
T5 has a output of approx 95-105 Lumens per watt (electronic ballast only).

High Output Fluorescent

•HO are basically the same as regular fluorescent except the ballast is designed to supply the bulbs with more electricity.
T5HO has a output of approx 85-95 Lumens per watt.
A 24 inch T5 NO is 14 watts.
A 24 inch T5 HO is 24 watts.
Power Compact (bent T6HO) has a output of approximately 75-85 Lumens per watt.
Higher restrike (when light hits another spot on the bulb and is lost)
Very High Output Fluorescent
VHO is basically the same as regular fluorescent except the ballast is designed to supply the bulbs with more electricity.
VHO has a output of approx 55-75 Lumens per watt.
A 48 inch T12 NO is 40 watts.
A 48 inch T12 VHO is 110 watts.

Compact Fluorescent

•Spiral bulb now used to replace incandescent bulbs and has an output of approximately 70 Lumens per watt.
Ballast is manufactured to be disposable
Ballast is not remote - life is shortened due to exposure to heat and humidity.
Very high restrike 
not a way to add a great reflector.

Mercury Vapor

•output of approx 50 Lumens per watt.
output spectra that is almost entirely blue-white, with very little red
High/Low Pressure Sodium
output of approx 100-150 Lumens per watt (currently the most efficient lighting system)
output is pure yellow (only good when used in conjunction with other types of lights).
New bulbs with increased Blue spectrum are now being used for terrestrial plants with great success, but have not been tried in aquariums yet.

Metal Halide

•Point source lighting is able to penetrate deeper aquariums (But lighting is less evenly distributed than with Fluorescents).
generates a lot of light in one spot, so more heat gets transferred into the aquarium water (fans and chillers may be necessary).
90 lumens per watt.

LED

•Dimmable many can reproduce sunrise and sunset (even the lunar cycle as well)
Longer life more than 50,000 hours
Virtually no heat transfer to aquarium water
Light is very directional (like laser pointer) optics(lenses) are necessary to spread the lighting
First led systems on the market are close to 90 lumens per watt.
Very Expensive Hardware.

Reflectors

•A good quality reflector will direct approximately 20% more light that is already being produced down into the aquarium.
David Stewart

Fishroom w/ 1000+ gallons with a little of everything, OK well still mostly plants Reply


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## Gizmo (Dec 6, 2010)

Aquarium Lighting for the Average Intelligent Aquarist:
Example: 24W 10000K 640nm Actinic T5HO

P=VI. A 24 Watt light plugged into a 120 Volt wall outlet pulls 0.2 Amps. A general rule of thumb for freshwater plants is 1-2 Watts per Gallon (WPG) for low light, up to 3-4 WPG for high light. Read further, however, as this is VERY subjective...

Ratings like 10000K refer to black-body radiation absorption, in Kelvin (absolute scale). Generally, this refers to the wavelength of light emitted.

Wavelength = Speed of light/Frequency (Lambda = c/f). Visible light ranges from 400nm-700nm. Blue light is approximately 475 nm, with red occupying 650nm. Plants thrive when absorbing wavelengths in the visible spectrum (400nm-700nm). Blue light is more intense but is lost faster in water than red light.

Names like Actinic, Daylight, GRO, etc. refer to specific temperature ratings and emitted wavelengths of light. See manufacturer spec sheets for details.

For fluorescent bulbs, the quality ranges from best to worst as follows: T5, T8, T12, and VHO, HO, NO. Similarly, it goes LED, Metal Halide, T5HO, Power Compact, Fluorescent. Cost is proportional to quality. LED is top of the line, both for efficiency (lowest power consumption) and quality of light emitted, but is also the most expensive. 130W PC is equivalent to 48W T5HO, then 32W MH, and ?? LED (research is still marginal for LED's).

For a light fixture to be effective it must combine a high-intensity high-quality-emitting bulb with a good reflector to direct the light down into the tank. A bulb with no reflector emits less than a quarter of its full capacity into your tank, with the majority being absorbed by the fixture.

The true measure of light intensity/quality is known as PAR, or photosynthetic active radiation, and is only measurable with a light meter. It is a measure of the number of photons per unit surface area per second and applies to photons emitted at frequencies only in the visible spectrum. A general rule of thumb is that 30 PAR at the substrate level of the tank is classified as low light. Plants enjoy light levels ranging from 20-80 PAR. Lux meters are less expensive light meters and their units can be converted to PAR by dividing Lux by an appropriate conversion factor for the specific light bulb being used (see manufacturer spec sheet).

Application to Aquariums

Fish only Tanks
From a color temperature standpoint (Kelvin rating): 
Blue-colored light (10,000K) will enhance blues in your fish. 
Green-colored light (5,500K – 6,700K) will make the tank look bright to humans and enhance the green color of your plants. 
Red-colored light (2,700K) will enhance the reds in your fish, and any red plants.
The light cycle can be important to trigger spawning (or a change in the light cycle).
The amount of light can be used to control algae.

Planted Freshwater
For green plants the lighting peaks that are most important:
– Chlorophyll-a: 430nm/662nm
– Chlorophyll-b: 453nm/642nm
– Carotenoids: 449nm/475nm
Red pigmented plants use more light in the blue area (450nm) of the spectrum.
If your lighting looks extremely bright and your plants seem ultra-green, it means that you have lighting that outputs strongly in the green spectrum.


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