Why is All This So Important?
We divide the aquarium lighting parameters into three things. Now get this; as EMR, this includes light approaches/enters into a more optically dense medium, in our case water, a couple of things happen.
1) a couple of is reflected depending on the angle of incidence, and disruption of the water surface.
2) EMR entering the water is refracted or bent as it is slowed, as water is more optically dense than air.
3) That light is selectively absorbed , the majority of the red-end of the spectrum, being filtered-out in the first few inches (tens of centimeters) of depth, with blue to UV +and beyond wavelengths reaching furthermore down. (Let’s dispense with diffraction, interference, polarization, etc. characteristics of light.)
The helpful biological implications of these facts are profound. Aquarium plants and other photosynthetic organisms utilize light-capturing mechanisms in the sort of photosynthetic (“putting in association with light”) pigments , like chlorophylls. The entire organic world runs on the energy translated and stored in photosynthesis. The conjunction of water and carbon dioxide (under favorable light, heat, nutrient conditions), re-formed as sugars and oxygen photosynthesis . The reverse of this reaction is respiration.
The loads of light-using species can only utilize certain wavelengths/frequencies of light ; markedly in the orange-short red and blue parts of the spectrum, not the green and yellow that our eyes most appreciate. What does this mean? If optimizing health/growth of aquatic life is your objective, you need to provide energy of the needed/useful wavelengths. Other spectra can be desirable for appearance sake; others (UV and infrared) might be innocuous to adverse to you, your system and your livestock. Thus the quality of light is critical.
What is the another aquarium lighting parameters? How about the quantity of light? This is, needless to say as meaningful as quality. Too small or too much light is hazardous.
The duration, how long the light is on daily is our last light concern. Plants that hail from the tropics experience a more permanent light regimen than ones from colder climes. Optimum conditions utilize an increasingly light morning to intense midday to decreasing afternoon, for slightly more than half-day light.
These three choices of light, quality, quantity and duration are chief concerns of the Conscientious Aquarist, indeed all aquarists. Thus we will cover them one at a time.
The final section of our debate will ‘throw light’ on recommendations of the expenses of function versus gives the impression in lighting the marine system.
1) System Light Quality:
The quality of light is its composition, mix of spectra (wavelengths), or color, if you will. Let’s review the leading measures/features of light quality, for you to make apples-to-apples comparisons for yourself concerning the various signifies of lighting your system(s).
Color Rendering Index (CRI) is an indication of how a light source impacts the appearance of a standardized color chart compared with natural sunlight (under controlled conditions). needless to say, sunlight scores a immense 100 CRI, with numbers approaching one-hundred being approximately sunlight. See the accompanying chart for what the sun’s spectral power curve approximates. For the sake of photosynthesis in aquaria, CRI values of ninety (90) or larger are called for.
Color Temperature is a more complicated concept to elucidate. For our purposes, let’s just mention that this is an equivalent temperature of a celebrity (like our sun) that would emit the radiation measured. Our personalities sunlight ranges somewhere between 5,000 and 6,200 degrees Kelvin. We need a light source of 5,000 degrees Kelvin (some writers mention 6,000) or larger along with a CRI of 90 or larger. Make sense so far? permit me re-emphasize; the pretty color rendered by “aquatic fluorescents” has nothing to do with functionality. You need a CRI of 90+ coupled with a Color Temperature of 5,000+ Kelvin.
A note here on Spectral Shift. As they are used, all the differing light technologies change to known degrees in the percentages of what wavelengths they generate. Their luminosity decreases in addition, in conjunction with the preponderance of the desired spectral bands. We’ll have more to mention about this later, but what you’ll need to provide and make adjustment for is that light quality degrades through use/time with all lamps.
2) Light Quantity
Otherwise known as intensity or photo-strength, the number of light is just as critical as its quality. Light quantity is measured in lumens, the International Standard of emitted light . Please discard the terms foot candle, and lux (ten foot candles). These are archaic choices of received light and not of much real use to the Conscientious Aquarist.
I’ll go out on a/the proverbial limb and offer a common “rule of thumb” for how much light is sufficient, to approaching optimal, to more than might be useful but not hazardous. My hesitancy consists of not knowing multiple factors that strongly impact your system’s light requirements. Tall tanks (greater than twenty inches) need more light. Ditto for ones with plenty of life, mainly ones with mechanical surface disrupters (pumps, bubblers), staggered, shady decor agreements, dissolved color, particulates….
Different photosynthetic species., accustomed to differing conditions and traumas have differing light demands. Water color, carbon dioxide, carbonate, pH, temperature… and more in addition change the minimum/maximum adviced lumens. Be all the things that as it may, I recommend one to two watts of full-spectrum fluorescents, close to equivalent to 50 to 100 lumens per gallon for most systems (sight unseen). For “super-systems” with C0 2 infusion, pH monitors/dosimeters, mega-algae and/or light-demanding plant species, copying (and then some) this number is not unrealistic. One last comment re the above.
Be aware that the watts of energy consumed is not equivalent to watts of light energy generated. Luminous efficacy, the light output divided by the power rating of the lamp, expressed in lumens per watt, is an important choice. The waste heat from other lighting formats is largely the lost part of this equation. You do not want to buy this waste-heat, it’s consequences, or deletion.
Lamps have rated life and lumen depreciation. The latter explicates the loss of light production through the life of a lamp; all lamps generate less light as they age with use. Rated life is a value determined by experiment. It is the time in which half the test lamps burn out; this is much more than their functional life span . 4 foot fluorescents are good for @ 20,000 hours, shorter lamps slightly less time. This translates to a good two years of 12-13 hours per day. Turning the lamp on/off generally shortens real and functional life. The usage of electronic ballasts extends the same. HO, VHO (Very High Output) and metal halide lamps undergo much more rapidly and severely from lumen depreciation and rated life, as much as forty percent loss.
3) Light Duration:
Also known as light-dark cycle, photoperiodicity; it is the number of time day after day the light(s) are on. Most photosynthetic organisms used in aquariums develop from the tropics where day lengths do not vary much throughout the year. Within factor, 12-16 light-hour days are optimum, more mainly if your quantity of light is on the low side. This is absolute determined by knowing what healthy specimens look like when provided appropriate lighting.
Regularity of photoperiod can be highly meaningful. Experiments have shown that long dark or light periods (1-2 days) severely impact aquatic life, photosynthetic and otherwise.
Use of Timers: Get them, they’re great; and fixtures with self-starting attribute.
Real fancy systems actually mix different quality and quantity light types as the day progresses. One such schema involucres a blue to red midday:
Lamp Type/Model # /Time On Off
Philips/ 82 / 7:00 – 16:00
Osram/ 41 / 8:00 – 16:30
Osram/ 41/ 9.00 – 17:15
Philips 83 ten:00 – 18:00
Some scientific culture laboratories even go so far as to utilize polarized light and lighting fixtures that travel overhead in an arc in an effort to more fully back up Mother Nature. Pretty awesome, isn’t it?
By Robert Fenner
Reprinted with permission, from Bob’s website in San Diego: www.wetwebmedia.com