Aquarium Lighting

[KaLiB]

http://www.geocities.com/ptimlin/lighting1.html

Article on aquarium light. Relatively good read for those who are new to this.

some more articles:

http://reefkeeping.com/issues/2002-08/dw/index.htm
http://reefkeeping.com/issues/2004-0...ture/index.htm

This is written by Gary Ahlers:

Reef Aquarium Lighting

There is a lot of confusion about what lighting is “right “for corals. Almost every hobbyist has his or her own opinion, often diametrically opposed. Even experts only have a varying degree of agreement and often contradict each other even in statements of supposed fact.

Improved technology has had a major impact on reef husbandry making it possible to grow and propagate even the most light demanding corals in captivity. Unfortunately the “more is better” philosophy is becoming ncreasingly popular. Watching the Internet B.B.s, I’ve seen a trend towards constantly upgrading to the next bulb wattage. It is not uncommon to see 180 gallon tanks lit with 400w or even 1000w MHs – after all, if 250s do a great job just think how good 400s will be!

Aquarists are routinely lighting their tanks with extreme overkill. This is both costly and can be detrimental to the health of the inhabitants. One guy was moaning that he put a 400w MH six inches above his 29 gal. tank and verything died. Can’t imagine why. What I will try to do here, is boil down almost three hundred hours of research and extract the most relevant conclusions as well as the reason for these recommendations.

First we need to set a few technical definitions:

Lumen – a unit of light striking a one square foot area of a sphere, 1 foot in radius with a point light source at the center. The total light from that source would then be 3.14 L. This is the standard for measuring artificial lighting.

Lux – equals one lumen striking an area of one square meter. This is standard for measuring sunlight intensity.

Kelvin Temperature – The temperature at which a body of matter will emit a given spectrum of electromagnetic radiation – light. 0 degree K equals –469 degrees Fahrenheit.

PAR (PPFD) – photosynthetic flux density. A measure of the light radiation available for use in photosynthesis

Fish only aquariums, which were the standard until the mid eighties, were easy to light. The fish lived in a spartan environment of dead rock and crushed coral. They only needed enough light to find food. With the advent of FOWLR and Reef Aquariums it was a whole new ballgame. Now you needed enough light to fuel photosynthesis based ecosystem. The questions were what kind of light, how much light, and how long. In each case we must also address the issue of too much or too little.

Light Quality

Sunlight, at the equator, at noon, has a full spectrum temperature ranging from 5,800 to 6,500 deg. K. This is not constant, but rises from about 5,000 in the morning and lowers again in the late afternoon. The light temperature (K) rises rapidly as depth increases because seawater selectively absorbs lower energy red and green light. An eighty feet the light temperature is as high as 30,000 deg.K.

Most photosynthesis by algae, plankton etc. takes place within the first several feet of the surface since green chlorophyll responds best to the red green and yellow portions of the spectrum. Agricultural grow light usually uses 4,000 – 5,500 deg K bulbs. This is a problem in an aquarium since it tends to overgrow the reef coral with algae. Higher temp light inhibits algae somewhat and stimulates coral zooxanthelle and coraline algae.

Corals are collected from about 6” under water to about 60 ft. . The majority of specimens are collected from the 20 – 40 ft. range of depth because of the greater diversity found. The light here is about 10,000 dig K. The optimum light spectrum, then, should be between 6,500 and 10,000 deg K for most coral species.

I have an ongoing experiment in this context – two 100 gal. tanks in a cascade water system. Tank 1 lighted with 6,500 deg. K - N.O. fluorescent. Tank 2 lighted with 50/50 URI - N.O about 7,100 – 7,500 deg K. fluorescent. Tank 1 is overrun with green algae and has to be cleaned every week. The coraline growth is very slow. In tank 2 there is virtually no green algae and coraline growth is luxuriant.

Duration

I have seen recommendations ranging from 8 to 14 hours, including one expert writing “ NO MORE THAN 9 HOURS”. As is often the case, most reefkeepers stay in the middle range – 10 to 12 hours. This is not the end of the story though. Sunlight changes light spectrum and intensity through out the day. Technology for varying a lightsource spectrum is not available; however, we can modify the intensity.

Quantity

According to GARF.org any coral can be raised and flourish under standard fluorescent. Another aquarist uses 2 - 1,000 watt metal halides over a 180gal tank. Of course, at the end of the text, you find that they always planned to upgrade slowly to VHO or metal Halide.

Let’s start with some measurements:

Peak sun at the equator (under clear sky) measures around 130,000 Lux, which equals 13,000 Lumen/sq.ft.
Directly under the surface this drops to 70,000 Lux or 7000 Lumen. This loss is mostly due to reflection.
At 1 meter (3.3 feet), 26,000 Lux or 2,600 Lumen.
At 30 feet, 15,000 Lux or 1,500 Lumen.
Light levels in early morning and late afternoons are 10x less than peak Lux.

It would seem that proper illumination would be 7 to 8,000 Lumen/sq. ft. for high light corals, 2,600 to 3,600 Lumen/ sq. ft. for medium light corals and 1,500 to 2,500 Lumen/ sq. ft. for low light corals. I found this to be in line with most Expert recommendations.

Continue from previous....

Rules of Thumb

Watts/gallon rule: 1.5 to 3 watts/gallon for low light, 3 to 5 watts for medium light, 5 to 7 for hi light up to 10 for the most demanding acropora sps., anemones and clams. This rule has been around for many years and has become questionable with the advent of CFL and MH lighting.

Different lighting systems vary greatly as to output per lamp:

50 Lumen/watt - NO Fluorescent 300w would produce 15,000 Lumens, loosing 10% at half-life of 10,000 hrs.
56 Lumen/watt – VHO Fluorescent 300w would produce 16,800 Lumens, loosing 30% at half-life of 4,000 hrs.
85 Lumen/watt – CFL Fluorescent 300w would produce 25,500 Lumens, loosing 30% at half-life of 6,000 hrs.
75 Lumen/watt – Metal Halide 300w would produce 22,500 Lumens, loosing 20% at half-life of 5,000 hrs.
85 Lumen/watt – HQI Metal Halide 300w would produce 22,500 Lumens, loosing 20% at half-life of 5,000 hrs.

VHO turns out to be only modestly more efficient than NO, but is preferred because of the number of tubes that can be packed into a canopy.
CFL are nearly as efficient as MH but lack the hot spot intensity because the output diffused over a linear dimension, a problem common to all fluorescent bulbs.
MH is a point source producing high efficiency and intense output.
Lumen/watt, spectrum drift and useable lifespan can vary by more than 25% depending on bulb manufacturer and type of ballast used.
All of these bulbs produce pretty much the same waste heat. It is just more or less concentrated by the bulb dimensions

Changes in tank setup have also added problems. A 250-gal tank with a 6-inch sandbed is really a 180 gal tank only 18 inches deep.

In order to obtain the maximum Lumen output all bulbs need to be installed in individual, parabolic, specular reflectors. These reflectors will increase output by as much as 270%. Having multiple lamps in one reflector increases bulb heating and restrikes. This will lower lumen output output and shorten bulb life.

Yet another rule, specific for MH lighting, is on lamp for every 2 feet of tank or 4 square feet of surface area. The bulb wattage is determined by tank depth – 175w for up to 18 inches, 2 50w for 18” to 36”, 400w for 24” to 36”, and 1,000w for over 36”. This seems to be a very vague guideline.

A more recent rule is Lumen/square foot of tank water surface: 1,500 to 2,500 Lumens/sq. ft for low light corals, 4,000 to 5,000 for medium light corals and 7,00 to 8,000 Lumens/ sq. ft. for light loving corals clams, etc. Sounds familiar, doesn’t it?

Even this rule has some problems. If you light the 180 gal tank by this rule the proper selection would be 4 – 250w MH (10 CFL) or 80,000 Lumens (7,000/sq. ft.). Remember, though, a MH is a point source. The square foot directly below the light will actually see 12,000 lumens – a bit much even for anemones. Mid light corals will go on the bottom third and don’t try low light corals except on the bottom. I won’t even mention the electric bill for cooling the tank and running the lights.

The final, actually the first, consideration is tailoring the light output to the corals. What corals do you plan on keeping? Low light mushroom, cryptic sponges, soft coral, LPS, SPS. All have their own needs and will perish if ignored. Too much light will kill as surely as too little.

One solution is to limit your specimens to those with the similar lighting requirements. Unfortunately, most aquarists use a gardening approach, picking their animals by personal preferences as to color, shape or even strangeness.

Conclusions

Can we create our diverse coral garden without sacrificing the health or life of these animals? Happily, with a little ingenuity and a lot of attention to detail, the answer is yes; you don’t even need to take out a second mortgage.

Starting with a 250-gal 96”Lx24”H x18”W tank we build up the substrate 6 inches. This gives a tank depth of 18”. Since the greatest variety of corals come from around 20 feet our main lighting should be 10,000K MH with supplementation by 6,500K fluorescent. 100% fluorescent is too diffuse and uniform for our garden.

The hot spots from 250w MH are way too intense for most corals in the upper levels of our tank Instead, why not use that that point source characteristic to our advantage. Lets go with 175w MH, or better yet, 150w 10,000K HQI. Now the center square is getting 7,800 Lumens while the tank bottom sees 1,950 Lumens. The pendants will be mounted 10” above the water and the entire canopy shielded with tempered glass. Now, all those different specimens collected from different depths can be happy living together.

Let’s go a little farther. Add 4 – 95w 6,500K CFL fixtures to even out the lighting and give a spectrum boost to the shallow water corals. With all these lights we can start staging on and off times to simulate sunlight conditions. When all is done you should be averaging less than 600 watts per hour and still have a 12 hour photoperiod. You’re using all electronic ballasts, of course. Now everyone can be happy. Even when the electric bill arrives!

Final Thoughts

Everyone acclimates their animals to the new water environment, slowly changing their water to prevent shock and stress. How many of us consider acclimating to light. When you take home a new coral it has been at least three different places as well as dark bags for many hours while traveling
around the world. You place it carefully in your tank and turn on the stage spotlights . The poor thing never had a chance!

Most coral are pretty flexible but they need time to adapt. This can take up to 2 weeks. Meanwhile they need protection. This is not a problem in the beginning. When the tank has been up for a year or so, you’re going to stress out everyone by playing with the lights. Set up the reef to have areas at the edge of the MH lighting squares with shading or even a cave. You can use this as a nursery to slowly bring your new acquisition into the light.

An acclimation tank is another solution. It doesn’t have to be fancy or even be running all the time. When you are planning for a new animal, fill a 10 gal with water from the main tank, throw in a power head, heater and several pounds of live rock and you’re all set. The light doesn’t have to be fancy either – a 150w brite white incandescent flood hung as a pendent will do – you’re acclimated for light intensity.

I chose 150 HQI pendants because they produce the same lumens as a 175 standard MH and have almost the same Par. Inexpensive electronic ballasts are available which run cool, produce about 10% more light, extend the bulb life and color stability. They also consume only 10watts more than the bulb giving them an operating efficiency of 95%.

HQI bulbs should be changed at about 60% of rated life - 4,800 hours – every 18 months – one at a time please! Raise the pendant to 18” during the initial 100-hr burn in.

There is a lack of data on aquarium bulbs that looks like an industry wide conspiracy. No manufacturer supplies specs as to lumens (initial and mean), Par or lifespan. They routinely supply them for every other bulb they make. Even the spectrum numbers are arbitrary. According to Sanjay, the actual bulb temperatures are often two or three thousand degrees off. AB produces a bulb designated 10,000K but actually runs at 13,000K initially. They kept the old designation for marketing. As far as you and the LFS know it’s a 10,000 K when you buy it.

HQI bulbs generate significant UV-A, B and C. A shield is needed to Reduce the UV-A and eliminate the UV-B and C. You want a shield anyway to protect against splashes and spray (HQI and MH bulbs operate at 3,000deg.F and can explode violently). Tempered float glass does the job very effectively.

All lighting needs to be vented to remove heat emitted by the bulbs and ballasts. Several methods are used. Passive venting in the fixtures and small fans pushing and pulling air in the canopy. This will, of course, move some of the heat away from the water surface. Unfortunately it requires you to run air conditioning to remove that heat from the house. BTW air should not be blown over a metal halide bulb – it both changes the spectrum and shortens the life of the bulb.

The most cost-effective method is to enclose all lighting in a canopy that is vented to the outside. If vented to the roof the system can be entirely passive All shields can be removed from the individual lights and replaced by one sheet of tempered LOW E glass on the bottom of the canopy. This glass will eliminate both UV emissions and at least half of the infrared.

There are three new technologies that look promising in the near future. LED, Fiber Optic and CCFL. Both have a unique advantage of putting light below the waterline without heat or infrared. This would allow all bulb output to be in the water column. Fiber Optic looks more promising and cost effective at the present time

Note: There may be some formatting or typo error.

Finally got a chance to read this great article... does that mean 400w MH is really a overkill? If the experiment conducted by the author is true, most sps are not exposed to lights of that high intensity....

now i start to worry if my 2x250W is too much for lps anot..

If they are control by individual switches then you can just on one lite instead of two.
That should half your lite immediately

Regards
Sherman

Originally Posted by ReDDeviLs

now i start to worry if my 2x250W is too much for lps anot..