Fluorescent Lighting Systems

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Fluorescent lamps are the most affordable and convenient solution for most beginning reef systems, and they come in standard output, high output (HO) and very high output (VHO) types. Brighter than standard lamps of the same length, HO and VHO lamps consume correspondingly more electricity. They also lose output faster, but this may be offset by periodic replacement. Output ratings tor fluorescent lamps discussed in the aquarium literature seldom refer to the efficacy of the lamp, i.e., the lumens of light produced per watt of electricity consumed. While it is generally true that "the higher the wattage, the brighter the lamp," the suitability of a particular lamp design for aquarium use has mostly been determined by trial and error. This makes giving precise watts-per-square-foot estimates of the amount of light needed for an aquarium of photosynthetic invertebrates a frustrating, difficult exercise.

As a starting point, select fluorescent lamps of the maximum wattage that can be easily accommodated over the aquarium. For example, if the tank is 4 feet long, use lamps that are also 4 feet long. Standard lamps in this length are 40 watts and provide about 2,000 to 3,000 lumens each, depending upon the lamp type. For moderate light in tanks up to 18 inches deep, two standard lamps are the minimum. (The single-bulb lighting strips commonly sold with "starter aquarium packages" are virtually useless for all but very dimly lit, nonphotosynthetic or fish-only systems.) Four lamps are needed for bright light, such as a lagoon tank. For a deeper tank, or to illuminate a tank more brightly with fewer lamps, HO or VHO lamps can be used.

For tanks up to 18 inches deep, use the following guide-

108 Natural Reef Aquariums lines for determining the total wattage needed when using standard fluorescent lamps:

Tank Dimensions LxllVxH linchesl

UUatts Needed of Standard Fluorescent Lamps

Minimal Reef Light

Moderate Reef Light

20 x 10 x 10 24 x 12 x 16 36 x 12 x 16 48 x 12 x 18

15 watts 40 watts 60 watts 80 watts

30 watts 80 watts 120 watts 160 watts

In order to thrive, virtually all soft corals and most stony corals will require multiples of this wattage, dictating the use of HO or VHO fluorescents, high-intensity compact fluorescents, or metal halide lighting. Additional illumination will always permit the maintenance of a wider range of shal-low-water species.

The nature of the phosphor coating on the inside of the white tube is what gives fluorescent lamps their spectral-output characteristics. Photosynthetic organisms have pigments that absorb strongly in the red and blue regions of the spectrum, although accessory pigments allow energy to be These are modest lighting levels, with the "minimal" gathered from light of many wavelengths. It is wiser to pro-wattage appropriate for fishes and nonphotosynthetic in- vide a balanced white light for shallow-water species and vertebrates. The "moderate" level can be sufficient for the to emphasize the blue wavelengths in aquariums for species less demanding soft corals such as Lobophytum, Pachyclavu- that come from greater depths. Most of the brand-related I aria y Sarcophyton, and even such large-polyped stony corals claims for fluorescent aquarium lamps revolve around their as Fungia, Plerogyra (Bubble Coral), Trachyphyllia (Open special spectral qualities. Hobbyists should remember that Brain Coral), Turbinaria (cup corals), and the Actinodiscus many combinations of fluorescent lamps have been suc-(mushroom polyps). Realistically, this calls for four fluorés- cessfully used to culture photosynthetic marine invertebrates cent bulbs above the tank, and even with this amount of and macroalgae. It is much more important to use enough light, many of these corals will suffer if the bulbs are not lamps to provide proper light intensity before fretting replaced frequently. minor differences in the spectral distribution curve of one brand of lamp versus another.

The fluorescent lighting system of choice among experienced reef keepers, assuming no budgetary constraints, would probably be two or three VHO full-spectrum or "reef" bulbs and one or two VHO actinic tubes for a 75-gallon tank, 24 inches deep.


Gallon Tube Aquarium

Good starter fluorescent lighting unit for a small reef tank, with oak hood enclosing two full-spectrum and two actinic-blue bulbs and a remote ballast unit.

Metal Halide Lighting Systems

The need for high light intensity, especially for larger aquariums or those featuring invertebrates that demand

Chapter Four 109

Metal Halide

plenty of light, is one reason I advocate the use of metal halide lighting. A single 175-watt metal halide lamp generates about 15,000 lumens and is smaller than a football. I know of no other practical light source for the aquarium that will provide this intensity in so small a space. A single-bulb metal halide pendant such as the one shown in the accompanying photograph is sufficient light to illuminate an aquarium of about 24" x 24" x 24" (about 60 gallons). A tank of this size, so illuminated, could be called a "brightly lit" or "shallow-water" tank, suitable for specimens accustomed to intense solar radiation. I have observed that many species of photosynthetic invertebrates grow and re- Metal halide bulbs, ranging widely in shape, size, and output, produce successfully in this level of illumination.

If you expand the cube to a rectangular shape 36" x 24" x 24" (about 90 gallons) using the same lighting, the level of illumination could be called "moderately lit" or "mid-depth." I have found that mushroom polyps, for example, will reproduce under these conditions, some other species will grow slowly, and many species are able to maintain themselves but do not grow or reproduce.

Finally, if you increase the size of the tank to 48" x 24" x 24" (120 gallons), still using a single 175-watt metal halide yield the most intense practical light for the home reef.

Saltwater Aquarium Solar Tube
Reef Aquarium Images

Simple and attractive with a remote ballast unit, a single-bulb metal halide offers intense lighting with good heat diffusion.

bulb for lighting, you would have a "dimly lit" or "deep" tank in which, for example, mushroom polyps would survive, but growth, if any, would be very slow.

The gold-standard reef lighting package today typically includes two 175-watt metal halide bulbs and two 110-watt VHO fluorescent tubes that can be operated

Excellent reef tank lighting package, with two actinic-blue flu- independently. Placed over a 4-foot-long tank 18 inches orescent bulbs and two 175-watt full-spectrum metal halides. deep, this lighting configuration will allow the aquarist to

Natural Reef Aquariums succeed with most soft and stony corals. Deeper tanks and more demanding stony corals, such as Pavona, Goniopora and certain Acropora species, need 250- or even 400-watt metal halides for success.

What about assertions that metal halide lamps will always "burn" invertebrates? This, in my opinion, is hog-wash. I have placed iiterally hundreds of specimens beneath metal halide light sources and have never had this problem. Even metal halide lighting will not be as bright as the sunlight that may have fallen upon these animals in nature. So where do these stories about burning come from? I suspect there are three sources for the confusion:

1. Some gorgonians and alcyonarians that are regularly sold as tank mates for photosynthetic corals come from areas where light intensity is naturally low. Placing such animals under intense lighting could well have detrimental effects. Try growing a forest fern in full sun and you will see by anal-ogy what I mean.

2. Some suppliers may not provide proper lighting for specimens kept in their holding tanks. If deprived of light for a sufficiently long period of time, polyps may shed their zooxanthellae, taking on a "bleached" appearance. When such specimens are subsequently reexposed to bright light, the remaining zooxanthellae begin to photosynthesize at a high rate and to multiply rapidly. This results in a high rate of oxygen production. While oxygen is essential for all forms of life, too much is harmful. Charles Delbeek has suggested that the detrimental effects of placing a bleached specimen under high-intensity lighting may be due to this oxygen poisoning.1

3. When corals and other polyps are held under conditions of inadequate light, or when the specimens happen to have been collected from shaded waters, changes in the pigmentation of the zooxanthellae result. Zooxanthellae are

1 Charles Delbeek, personal communication.

marvelously adaptable. They produce, in addition to chlorophyll, a host of other photosynthetic pigments. Some of these "accessory" pigments permit the utilization of light wavelengths that chlorophyll does not absorb, enabling the zooxanthellae to capture more of the sun's energy and to take advantage as much as possible of the light spectra available at different depths, on cloudy days, etc. Other pigments are produced by the host polyp in response to ultraviolet light and probably serve to shield the zooxanthellae from the harmful effects of this radiation.

Therefore, two things can happen when organisms harboring zooxanthellae are shifted from one lighting regime to another. The proportion of the different accessory pigments may change as the zooxanthellae accommodate themselves to the new light situation. This may be evident as a color change in the coral and be interpreted as burning by aquarists unaware of the phenomenon. Alternatively, organisms from deeper waters, or specimens that have languished for too long in dim light, may have ceased production of protective pigments. When these specimens are then placed under bright lights, the effect is similar to that experienced by someone who, having spent a long winter indoors, rushes out on the first sunny day and spends an afternoon sunbathing. I believe that the alleged burning of corals by metal halide lights can be attributed to a lack of understanding of how these organisms respond to light and not to any inherent detrimental effect of the lights themselves.

When in doubt, experts typically do not place newly acquired specimens close to the surface and directly under strong metal halide lighting. Rather, the new coral or other organism is started lower in the tank and gradually, over a period of days or weeks, worked up to the position where it will be permanently placed. ( Vegetable gardeners who start their own seedlings will see the similarity to the "hardening off" process used when indoor plants are first exposed to full outdoor sun. This is done over a period of days,

Chapter Pour as even sun-loving tomatoes can be seriously "burned" by sudden, day-long exposure to unfiltered sunlight. As with metal halides, it is not the source of the light that is the problem here, but rather the lack of experience oi the human manipulating the plant or animal.)

On the other hand, overheating is a real potential threat whenever metal halide lights are used. With good air circulation over the surface of the tank (usually provided by silent "muffin" fans that come on automatically with the halides), and a cool or air-conditioned house, increased water temperatures may not result. But metal halides do throw prodigious amounts of heat, and many owners of such lighting systems have found the need to incorporate chillers to prevent routine overheating or disasters during hot spells. Whenever installing a new lighting package, make frequent water temperature checks to ensure that a problem isn't developing. (Even HO or VHO fluorescents in a tight, un-ventilated hood can overheat certain systems.)

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  • daniel
    What wattage of lighting starter for a 4 foot aquarium?
    8 years ago
  • Girmay
    Which vallisneria in brackish tank?
    8 years ago
  • jaxon
    When to replace flourescent reef lights?
    7 years ago

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