lighting for reef aquariums.

For marine aquariums lighting, the process of Chlorophyll synthesis has to be considered being that it is the chemical reactions and pathways by the plant hormone cytokinin once exposed to the correct nanometers wave length at around 670 NM of light allowing the formation of chlorophyll, resulting in continued growth of a plant.

This gives the algae-zooxanthella the ability to "feed" and propagate, and without this aspect PAR of 670 NM light energy or there about, zooxanthellae and plants will fail at these two actions!

The results of the lack of this high PAR "spike" would be the stunting of freshwater plant growth, and eventually poor coral health in reef tanks do to the cells of corals symbiotic plant life.

It is also noteworthy that Fluorescent and even more so incandescent lights produce a lot of yellow and green nanometer light, which research indicates is mostly wasted energy in terms of the needs or freshwater plants and SPS Corals. This is where an LED aquarium lamp,Metal Halide, or even (to a lesser degree) T2 Lights excels as there is much less wasted yellow/green light.


Photons at shorter wavelengths (Ultraviolet –C or UVC) tend to be so energetic that they can be damaging to cells and tissues; fortunately they are mostly filtered out by the ozone layer in the stratosphere. Green light occupies the middle spectrum (550-620nm; what is mostly visible to us) and is partly why chlorophyll is green due to the reflective properties.

Bulbs that emit mostly actinic light will have a lower PAR (although actinic UVA still occupies a spike in PAR as seen from the graph and improves the PAR of your lighting), bulbs that occupy mostly the middle spectrum (yellow-green) such as "warm White (2700- 3500K ) will produce little necessary PAR, while bulbs that produce mostly infrared (as seen from the graph) will produce more important PAR light energy, however it is the balance of infrared and UVA that will generally give you the best PAR output.

Lights out time for reef aquarium life.

Never have your aquarium, “that is a confined area” with no lights on!
By that I mean have something like a reasonable moonlight type of thing going24/7 and obviously the usual photosynthetic lighting period as well.
Lights on from around 6.00 am till 10.00 pm and maybe at the back of the aquarium have a low wattage led light going while the main lights are off.
Fish do fine when they can swim around and see, 24/7.
You see marine fish don’t sleep as we do, they rest and they can do that any time they want to, with eyes open of course,lol, they don’t have eye lids and in a reef tank, “not in some tanks if they do not use live rock” there may be many hitchhikers like crabs,worms,brittle sea stars and more. These crawl around at night and when these touch your fish, at times, the fish shit them selves and its either out over the top edge they go, or run into a coral or live rock or an anemone or if they are lucky, they run into nothing and its all good.
The most prolific killer of our aquarium pets being stress, and a segment of that is called the fight or flight response. So at night, when they can not see and when in an aquarium they can go know where, then that stress is unbelievably damaging at time of,oohh what just touched me?

Lighting terms and their meanings.

NM-
Visible colour spectrum wavelengths with in the nanometer scale.
All light energy is measured on a "nanometer" (nm) scale, this means a nanometer scale is used to measure the wave length of light energy from cosmic rays to radio waves, also nanometer means (one-billionth of a meter).

These are the nm-nanometer colours and at what part of the scale each colour occurs:
Violet is at 400 to 420nm
Indigo is at 420 to 440nm
Blue is at 440 to 490nm
Green is at 490 to 570nm
Yellow is at 570 to 585nm
Orange is at 585 to 620nm
Red is at 620 to 780nm
These wavelengths determine how the wave affects the aquariums inhabitants.
It is this wavelength difference that allows short-wave x-ray to pass through walls, while longer-wave visible light cannot pass though the same material; short-wave ultraviolet and x-ray can destroy DNA in living micro organisms and breakdown organic material while visible light will not.

PAR-
This should be PUR (photosynthetically useful radiation).
Uvr has been found to be totally useless in a reef tank due to the success of  LED marine aquarium lighting which has no UVR!
PAR is the abbreviation for Photo synthetically Active Radiation which is the spectral range of solar light from 400 to 700 nanometers.
This is supposedly needed by plants & symbiotic zooanthellic algae plants for photosynthesis.
This is found from actinic UVA to infrared.
UVA is between 400-550nm and 465 to 485 has the highest PAR of the actinic range.
Low (near) Infrared is 620-720nm,which is the red absorption bandwidth of chlorophylls A and c².

Measuring PAR
Kelvin as well as LUX conversions using questionable LUX to PAR conversion factors are ways of getting rough estimates of PAR.
Only a Specific PAR Meter (also called Quantum Light Meters) can give you the best measurement of this very important aspect of determining your tanks lighting requirements (both at the surface and under the surface).
• PAR (often easiest determined by Kelvin output), although it is important to note that the symbiotic zooxanthellae found in many corals and clams require more of the "blue spike", so high PAR for higher plants is not exactly the same for corals although it is safe to say a PAR reading of 50 mmol will work for most light sensitive corals.

If you research your Kelvin and NM ratings, this will suffice and the par reading is not essential.

K-Kelvins
This literally dictates the aquarium water depth that your lighting can achieve.

Kelvin is used in the lighting industry to define the Colour temperature of a bulb. Higher color temperature lamps above 5500 K are "cool" (green–blue) colors, and lower color temperature lamps below 3000 K are "warm" (yellow–red) colors.

Plant chlorophyll absorbs light at wavelengths of 300 to 700 nm (a Kelvin rating of about 6400 strikes a good balance here, which is why this is the best Kelvin temperature for freshwater plants and symbiotic zooxanthellae in corals).

The lower the "K", the more yellow, then red the light appears, such as a 4500 K light.  The higher the "K", the bluer the light appears, such as a 20,000 K light.

Higher Kelvin Color Temperature lights penetrate water more deeply, even more so in saltwater, however there is less of the infrared "PAR spike" as well.
The human eye sees mostly sees light around 5500K.

*The 6500 Kevin bulbs have produced the best freshwater plant growth (as this Kelvin lamp generally has more of the infrared nm spike need by "higher" plants, but still has some of the 425-500 nm blue).

This Kelvin Lamp can also work with SPS, LPS placed high in the tank water column (nearest the lights) based on the symbiotic zooxanthellae needs found in these corals. For more depth penetration (& to aid in the first blue spike in PAR, please see PAR section), blue actinic, 50,000 K/Actinic or adjustable/multiple LED can be added (such as Aqua beam marine blue ) can balance out 6500K lamp if used in marine reef tanks.

Please note that saltwater absorbs slightly more light energy than freshwater due to the higher density of the water, so 6500 will not penetrate as deeply.

*The 10000-Kelvin bulbs also achieve good growth rates, although slower than the 6500 K bulbs in shallow aquariums. 10000 K bulbs have produced excellent growth with soft corals and LPS, although slower paced SPS growth.

The 10,000K can be a good choice for achieving PAR for better depth penetration than a 6500K bulb (such as 20 inch or deeper aquarium)

*The 14,000K light/bulb (often popular with Metal Halide and LEDs), will penetrate even more than the 10,000K light while still providing useful PAR (this would be the highest "Daylight" Kelvin temperature I would go for and still expect good growth in corals.

*The 20,000 K bulb is more blue yet and brings out all of the fluorescent pigments in many corals (making for a very nice appearance).
However the best tests and observations show that when used alone the growth rate of SPS corals can come to a complete standstill with 20,000 K lamps. Although a good supplement for appearance and deep tanks, these bulbs generally should not be used as the only reef Kelvin temperature and should be avoided when used as the only Kelvin temperature lights (with the exception of some MH 20,000K lights)

*The 50,000K is generally the Kelvin rating of an actinic blue light source which is beneficial for the first "spike" in PAR. This temperature light (as with 20,000K) is best used with other light Kelvin Temperatures and is a better choice than the 20,000K light for such combinations.
The 50,000K is a good compliment to the 6500, 10,000, 14,000 Kelvin lights, especially for zooanthellic algae necessary for stony corals, clams, nudibranch, anemones, and other sessile species.

Sunlight just after dawn is about 3500 K
Typical summers day is about 6500 K
A cool white fluorescent is around 4200 K


Lumens

The international unit of luminous flux or quantity of light used as a measure of the total amount of visible light emitted. The higher the lumens, the "brighter" or more "intense" the light looks to the human eye. You can figure lumens per watt by dividing the lumens your lamp lists by the wattage the fixture lists.

When choosing aquarium lighting the general rules are-
Firstly LED lighting surpasses all resistance lighting!
T8 lighting for depths of 12inches of aquarium water.
T5 lighting for depths of 16inches of aquarium water.
T2 lighting for depths of 18inches of aquarium water.
LED lighting for depths of 24-30 inches of aquarium water.
Metal haloid lighting for any greater depths of aquarium water.

LED lighting-
One watt LED fittings should be 120 watt or greater for corals.
Three watt cree LED fittings should be from 90 watt or above with 60 degree LEDs for the best par rating.
The degree dictates the concentration of the beam as it is directed at the bottom of the aquarium.
                                                                                   
30 degree   Power full,spotting. 60 degree  High power,good PAR & coverage.

90 degreeMedium power,shallow good coverage.


The greater the degree the more spread out the light and a weaker result at the bottom of the aquarium, similar to a torches beam of light.
30 degree diodes will place spots on the bottom,60 degree will be just a wide enough beam to cover the bottom with out loosing concentrated light to give better PAR ,(depth penetration).

LED lighting can boast a comparison of four times the out put to actual used watts and no UVR that has been found to be detrimental to corals.

LED 3 watt diodes with in a 90 watt fitting is similar to a 250 to 300 watt metal halide in PAR.

Led lighting explained
https://southeastqueenslandm.aforumfree.com/t940-led-lighting-for-reef-aquariums-tried-and-tested-information-and-what-are-they?highlight=Led+lighting

Led light buy up
https://southeastqueenslandm.aforumfree.com/t2032-lighting-buy-up-from-china#8035