Anthony Calfo offers some insight on lighting for saltwater aquariums.

Lighting choices are some of the most important decisions you will make for your marine aquarium. Proper lighting schemes and their good maintenance over time are instrumental to the success of any display. They also consume a significant portion of a display’s budget to buy and operate. Shopping the many lighting options and products available may seem daunting at first, but rest assured that sense and solutions can be readily discerned to serve you best.

Some of the first questions that need to be asked are: what kind of organisms will be kept, and what are their specific lighting needs? Too often, aquarists get caught up in wonder and marketing claims in search of a fixture that fits their tank size and not their livestock’s needs specifically. The keeping of photosynthetic invertebrates like corals and anemones imposes certain demands on lamps and intensities. Systems without such symbiotic animals, however, will still require careful consideration of hardware beyond aesthetics for the cultivation of desirable plants and algae or attempts to prevent undesirable life forms (diatoms, cyanobacteria, etc). Numerous other organisms on and in common living substrates (sand and rock) are influenced with light quality in kind. Good decisions with lighting applications will help ensure that new aquarists start well, and that established aquarists fare better with keeping and culturing the most desirable marine creatures under attractive illumination.

Lamp color is the first grade in the decision making process. Light bulbs are rated and evaluated in a number of different ways having various measures of importance in different applications. “Color” or “temperature”, measured in degrees Kelvin (K), is perhaps the most popular unit in marketing and advertising. The spectrum of light is described on the warm end (red, orange, yellow) of the Kelvin scale with lower numbers, while cool colors (blue, violet) are assigned higher numbers. Most desirable aquatic plants, corals and algae fare best in light within the range of 6500 to 10,000 Kelvin. Undesirable algae and very shallow species are supported by warmer colors (below 6500K). Many lamps are known to stray toward this lower end of the Kelvin scale as they age, and may be evidenced by an increase in nuisance algae growth in the aquarium. Deepwater species and various cnidarians fare better in cooler light schemes (heavy blue color) in the range of 10,000 to 20, 000 K, while most plants and algae do not. You are advised to finesse the needs of your livestock within these guidelines when known, or make the conservative choice and stay between 6500 and 10,000 K for general-purpose applications.

Advancements in fluorescent lighting technologies in recent years have flooded the market with numerous choices of bulb types. Standard output (SO) fluorescents are essentially the earliest and most popular types of lamp used on modern marine aquaria for their common availability and because they are fairly inexpensive. SO lamps are efficient to operate and are available in a wide array of colors. Unfortunately, they have a very short useful lifespan for photosynthetic organisms at 6-10 months for most. Standard output fluorescents may be fine for very shallow water applications and low-light biotopes, but are too weak to be useful for many aquariums. More intense fluorescent bulbs of several different types are more effective and attractive in aquariums up to 24” (60 cm) deep. Very High Output (VHO) and Power Compact (PC) technologies have become tried and true strategies combining good color and energy efficiency. Lifespan for these more expensive bulbs is not especially envious, though, being quite similar to SO lamps. Nonetheless, they are some of the best and most practical forms of lighting for marine aquariums. A new technology on the market, T5 fluorescents, has shown even greater promise for efficacy and quality.

Mini PC light	Suspended Canopy

Although it is best to avoid generalized rules of thumb as primary influences on your decision making process, most aquarists find themselves using 4 to 5 watts per gallon of aquarium in their lighting applications. Where such guidelines do not hold up well, however, are in deeper aquaria and with demanding plants and invertebrates at depths towards 30” (75 cm) and beyond. In such circumstances, a more intense lamp will be necessary; metal halides (MH) are commonly used for such applications as they have the ability to penetrate water better than fluorescents. Most MH lamps are also likely to last longer (over 18 months) and stay truer in color (useful lifespan) than fluorescent technologies. The initial purchase price for MH hardware, however, tends to be more expensive. The merits and limitations of various types of lighting at length must be weighed against the goals you are trying to reach in your marine aquarium.

Once you have decided on a lamp color and type, be sure to optimize the delivery of your light into the aquarium with a good reflector. Numerous DIY reflectors have been used to line fixture housings, running the gamut from simple to sophisticated. The list of reflective materials commonly used is amazing and includes polished aluminum and steel, rain gutters, shiny hobby films (model planes), foil, and bright or light colored paints. Most all fall woefully short of an engineered reflector. Some fluorescent lamps are manufactured with a built-in internal reflector; these bulbs tend to be rather efficient. All bulbs though will benefit from the use of a parabolic reflector (angular, polished metal feature designed for the purpose. Always use the best possible reflector within the limitations of your lamp housing.

Horizontal MH Pendants

Lamp housings have evolved to become necessarily ingenious for the many needs and preferences of aquarists working on their aquariums in varied living spaces. Much could be written at length on the commercial variations of light housings, while DIY interpretations are even more bountiful! The three fundamental types of housing are: fixed, independent or hybridized. Which type you choose is mostly a matter of personal preference and aesthetics. Independent housings are generally reserved for the less intense light fixtures and include the traditional strip-light fixtures. They are most always self contained with a shell, reflector, lamp and protective lens all in one tidy package that sits upon the aquarium glass top or plastic lid and is easy to move if necessary. Aesthetically, they may not be as handsome as fixed pendants and finished light canopies, but they are convenient and usually the least expensive choice. Pendant fixtures (suspended from the ceiling) are usually installed out of necessity (space) or desire to make and aesthetic impact as a hardware feature. They tend to concentrate and focus light in a limited pattern like a beam and are not often the most efficient distribution of light. Suspended lamps are usually convenient and easy to work around, however, and are helpful in living spaces where heat (as with an enclosed fixed or independent canopy) is an issue. Enclosed, fixed canopies are the largest and most cumbersome forms of housing, but they usually offer the best distribution of light through the freedom of extra space for hardware. Novel adaptations for moving such large canopies to work on and around abound including tracks on bearings, piano hinges, pulleys and simple doors. Accumulated heat is sometimes an issue in enclosed housings but is easily corrected with inexpensive exhaust fans. Whichever housing you choose, try to keep the efficient delivery of light (via mounting and lamp positions) and optimal reflector options in mind with buying decisions.

The correct mounting of aquarium lamps is an oft-overlooked yet crucial aspect of lighting applications. Fluorescent lamps should be mounted no further than 3” (7.5 cm) off the surface of the water, while metal halide lamps are generally kept 6-10” (15-25 cm) off the surface (up to 175 watt lamps). Bulbs kept at even slightly greater distances can be significantly reduced in intensity and efficacy (measured in water at depth). A light meter can be very revealing regarding this dynamic and will also indicate waning lamp intensities for the efficient exploitation of lamp life. For large aquariums especially, a light meter is highly recommended (its also a wonderful aquarium toy for the technologically fixated!).

At last, light and canopy maintenance is a simple but necessary matter. Housings with exhaust fans will inevitably accumulate dust and debris quickly and require extra care to keep clean. Fluorescent lamps kept necessarily close to the water surface will also accumulate salt creep fast. All lenses and lamps should be wiped clean at least weekly to ensure a consistent and maximum delivery of light. It is remarkable how such a very small amount of debris can significantly reduce light transmission! A word of caution is warranted too for the fearless DIY aquarists: wiring and electricity are very serious matters, of course. Please be mindful of building codes for safety, and be realistic about your abilities with construction and wiring of DIY light fixtures and canopies. It is a very common mistake inside of custom canopies, for example, to forget to protect shielded wiring that is exposed within the fixture. The UV stability of wire shielding can become an issue over time; some coatings degrade from the prolonged exposure to intense light within the housing day after day and leave exposed live wires! Commercially constructed and professionally built fixtures are recommended. Seek the advice of your local merchants and fellow aquarists (online and at local aquarium clubs) to help you make an informed decision to suit your aquarium’s lighting needs. With kind regards, Anthony.

Suspended Canopy	Suspended Metal Halide Pendants

Anthony Calfo
The author of The Book of Coral Propagation, Reef Invertebrates, Anthony has been slicing dicing giant leather corals in his Mom's kitchen for years. After his family accidentally ingested a colander of Sinularia "Spaghetti Leather Coral" topped with their favorite tomato and basil marinara, he built an actual greenhouse to hone his propagation and growout techniques. Today Anthony spends most of his time writing and traveling the world, sharing his knowledge and enthusiasm for the hobby, happily branded with his own unique humor and sensibilities.