Bigger is not always better when it comes to reef lighting. Most corals are highly adaptable to a wide range of light. Hobbyists with traditional "garden reef" displays must lean towards the lowest common denominator while compensating with foods/feeding for photosynthetic species not fully satisfied by the compromise on lighting.

The topic of this rant… errr, of this article was inspired by conversations refined from a trip to the 2004 IMAC. Aquarium conferences and hometown club meetings are often so invigorating! The time spent listening to presentations, chatting with vendors, and especially conversing with fellow aquarists in sidebars (emphasis on bar, in many cases… but productive nonetheless) is priceless. Friends must surely tire of hearing me sing the praises of these events, but I strongly encourage my fellow aquarists to attend at least one aquarium conference or trade show per year. It is one of the very best ways to network, glean information from other, often well-traveled or well-read, aquarists, and to advance our knowledge of the hobby. The money spent really is an investment in your future success, beyond the gratification of education and the pleasure of fellowship.

Returning from Chicago, I was moved to put down these thoughts for consideration of one of the most challenging and controversial issues in the hobby: artificial lighting. My purpose is not to try to prove anything; I cannot do that here. I simply wish to give fellow aquarists pause amid the frenzied purchases and debates over lighting issues with a reminder that there is no definitive lighting solution or product to be found. I'm thinking of the poignant reminder from Dr. Shimek regarding Science, mentioned again at IMAC, to paraphrase here, "[Science does not aim to prove anything… but rather, it sets up two models and disproves one of them]." The issue of artificial reef lighting really cannot ever be "solved," but it will evolve in time.

Too much attention is paid, in my opinion, to obsessive debates over what is the "best" lamp brand or color for reef corals. Unless your tank is a natural biotope or specific niche, the concern may be moot. Coral farmers and public aquariums for over 20 years now have been growing corals very well under heavy daylight (industrial) lamps, 5,000 - 6,500 K. Many home aquarists have also found this to be true, with an emphasis on warmer colored bulbs when optimal growth of common corals is the primary interest.

Manufacturers and researchers continually spend an enormous amount of time and effort trying to improve lighting technologies. Similarly, aquarists spend an extraordinary amount of time trying to research, argue, defend, or determine what is the "best" lighting for a given reef aquarium. To all, I say, "Keep your eye on the prize." (a favorite phrase from another mentor of mine, the inimitable Bob Fenner). What is it that we are trying to prove? The goal in lighting your photosynthetic creatures is not to have optimal hardware… but optimal health of the animals themselves, by whatever means. Those means cannot be satisfied by summarily saying, "if you want to keep x coral, then you should have x lighting." It just does not work that way. The three dimensional environment of an aquatic system is influenced by many factors. Does anyone truly believe that any standardized lighting scheme could be "perfect" for the random and various organisms we collect from the world's reefs when we not only mix specimens from different niches or biotopes, but different oceans?

Case in point, lets say that you get an established coral from an aquarium with known hardware (lamp type, color and wattage) with a known measurement of light (in lux). Even by having the same type of hardware at home and placing the coral at a depth with the same lux reading, you still cannot guarantee that the coral will get the same illumination. The quality of light delivered can be affected by the age and temperature of a lamp, for example. And the penetration of water at any depth can be affected (filtered, refracted, etc.) by turbidity, clarity or action of water at the surface. Thus, the placement of x coral at a depth that has the same reading of y lux, under the same brand and type of z lamp, is still not guaranteed. We are at the mercy of some very common realities of aquarium-keeping here. What if tank A has an older bulb but better water clarity (daily ozone or weekly carbon use)? If tank B has a newer bulb but worse water clarity (i.e. more discolorants) can we succeed in getting the same lux reading at a given depth? Yes. Will the quality of light be the same? No. Is it a big enough difference to be concerned about? Perhaps... or perhaps not. This clumsy analogy speaks to the limitations of using lux, for example, as a unit of measure that so many aquarists beg for with the hope of bringing some fact or science into the debate about reef lighting. I think that if I hear one more hobbyist complain that there is no book or reference listing the "necessary" lux for all of the beautiful corals he wants to keep, I will laugh myself to incontinence. There are other factors to consider beyond lux readings.

Divert some of your energies away from debates about the "best" reef lighting, and instead to issues such as the physical delivery of light. Of special concern is maintaining optimal water clarity by regular carbon or ozone use and weekly cleaning of dust and debris from lamps and lenses. There are also some very novel, if not effective, methods for mounting and moving light systems, which are worth experimenting with.

Issues of water clarity and turbidity instead are grossly underestimated in my opinion. You can test for and quantify this with your systems easily - read on. In all my travels, and for all the aquariums I've seen through the years, it still surprises me to see expensive lighting systems trying to punch light though dirty lamps with water spots on them, through lenses and glass or acrylic covers with dust and salt creep, or simply through turbid or unclear water. Problems with turbidity specifically are relatively uncommon; few tanks actually have regular and persistent problems with suspended particulate matter. For those that do, know that it is a severe impediment to the penetration of light at depth. By comparison, we can look to some of the thorough research done on UV sterilizers to determine their efficacy (it is critical to pump only highly polished water through these units if they are to be effective at all). A pervasive problem that aquarists commonly face is water clarity, or discoloration to the water. How many hobbyists would you guess use ozone full-time to maintain optimal water clarity? How many aquarists change small amounts of carbon weekly instead of monthly (to prevent light shock or stress)? Some folks use no chemical media or ozone at all! I'm not saying that you need carbon or ozone to maintain optimum water clarity, but short of large and frequent water changes, there really is no practical alternative. Although your water may not look particularly yellow or discolored, rest assured that even a slight discoloration after a few weeks can reduce the penetration of light. If you have any doubts, just buy or borrow a lux meter and take a reading before and after an application of ozone or carbon. Its ironic that many aquarists spend so much money on fixtures, lamps and electricity, yet fail to keep up with simple maintenance tasks to maximize the use of light produced!

The issue of cleaning lamps, lenses and tank covers should be similarly obvious. Yet, in our busy lives, we often forget to faithfully maintain these, and subsequently handicap our light systems and photosynthetic creatures. I promise you that the reduction of light from any of the above mentioned obstructions is a far greater issue than the often subtle differences between a few months of age on a lamp due for replacement or even the choice between similar colors/brands of many bulbs. If you want to get the most "bang for your buck" with aquarium lighting, focus on maintaining your hardware and worry less over the search for magical lamps and measurements. Clean all lamps and lenses weekly for best results and minimal disturbance or shock to the illuminated organisms.

Having read this far, you might easily gather that I am not a big "fan" of using light meters. On the contrary, I use lux and PAR meters and strongly encourage most serious aquarists to buy or borrow a meter to learn fascinating and important information about the delivery of light. I preach to most every aquarium club I visit that they should invest in a unit for the membership to share for renting or lending out. Readings taken on new and aging lamps (reference points and tracking their performance degradation) can give an indication of when its time to replace bulbs. Non-believers in carbon use can find new appreciations in what was previously thought to be clear aquarium water. And the impact of just a little bit of dust or debris on lamps and lenses can really be underscored with a check of light intensity before and after a cleaning. Above all, though, use a light meter merely as a guide and not as a rule - much like an ORP meter. Redox (ORP) and light meters will help an informed aquarist tune and tweak his husbandry habits for better success overall - no more, no less.

It funny, but I still hear reservations to this day from aquarists and distributors who have fears or concerns about greenhouse grown corals acclimating to artificial lights. With all due respect, the logic behind this line of reasoning (or lack thereof) baffles me?!? How is it that corals collected from the wild, as most still are, differ from corals grown locally or regionally in a greenhouse? No doubt, wild corals stressed from collection and the rigors of import are less prepared to acclimate to artificial lighting than are soundly established, domestically produced livestock. This mention of farmed corals is a slight digression, but nonetheless still speaks to the real underlying issue: the adaptability of coral to a wide range of light. Folks with traditional "garden reef" displays must take advantage of this to have any hope of long term success. With a wide mix of species having different lighting needs and preferences, a hobbyist must lean towards the lowest common denominator and hopefully will not include terribly incompatible tankmates with grossly different needs or tolerances for light. With species requiring higher light intensities, the aquarist can compensate for the lack of light, and production from zooxanthellae, by extra feeding. Interestingly, the opposite approach does not work. That is to say, for example, corals that derive 75% of their nutrition from the products of symbiotic photosynthesis cannot be compensated for a lack of food (the remaining 25% of their daily nutrition from organismal or absorbtive feeding) with "extra light" (neither in duration nor intensity). Most all corals need to be fed regularly!

Unless one has a magnificent 20,000 gallon reef aquarium like the jewel at Atlantis in Riverhead, NY, there is no need for most aquarists to have banks of halides in sufficient numbers to dim the neighborhood's lights, melt live rock and make the sun envious.

Let's divert some of our energy from concerns, and especially debates, about the "best" artificial lighting and focus instead on the animals - not just the hardware. So many of the creatures we keep occur over a very wide range on reefs by a remarkable scale of magnitude (like Catalaphyllia elegant corals and some acroporids separated by more than 20 meters)! Yes… the same species, but profoundly different exposure of dispersed colonies to light. In such circumstances, the arguments over specific measurements of light becomes particularly moot, and the value of improved feedings (to compensate for deficiencies in light) and water flow (for better health/growth) become more apparent.

In a phrase, I think too much attention is paid to lighting issues. With the availability of several well-established lamp brands and types (time tested and favored by a consensus), I'm content to use and recommend bulbs such as Ushio, Aqualine, Radium and Iwasaki without obsessing too much over minutia. Furthermore, with most aquarists keeping "garden reef" tanks with unnatural mixes of corals (high species numbers and concentrations), expectations for optimal results with all specimens in the display is plainly unrealistic! There are some generalizations about light that a majority of aquarists can (maybe) agree upon. Take them as my opinion and nothing else. Lamps with a higher PAR rating and color closest to daylight (basically the 6500 K bulbs) tend to support the fastest growth among commonly kept species in the trade. Deeper water zooxanthellate cnidarians with pigments that fluoresce attractively (i.e., corallimorphs, Fungiids and other so-called LPS species) seem to keep very well under bluer lamps (20,000 K bulbs). And the ever popular (with good reason) 10,000 K lamps seem to offer a nice balance between growth and aesthetic color for most popular species. Again, these are only gross generalizations… yet the overwhelming majority of aquarists are not housing biotope displays, and thus have no right or reason to expect a tailored solution for lighting challenges over garden reef displays.

Finding good reef aquarium lamps is not difficult. Data from manufacturers and independent studies alike are easily found on the Internet and elsewhere. If you have a mixed garden reef display, then your choice is easy - buy most any reputable brand like Ushio or Iwasaki, because no lamp in existence could possibly optimally support the random and various mix of corals in everyone's tank. Improve coral growth otherwise with improved feeding and water flow.

So we come back again to the issue of adaptation, or acclimation. It's the dead horse that I'm trying to beat here. The recurring theme: please, please, please - quit obsessing over the search for the "Holy Grail" of reef lighting. It does not exist. From the advice above and an intelligent consensus from other sources, pick a reputable light system from an established company and be content with your choice. We can then focus our energies on better ways to acclimate corals. For many years I've been recommending a favorite technique called the "screen method." This is not rocket science, my friends. Rather than start new corals at the bottom of an aquarium and work them slowly up the reef to their final destination, as has been the tradition, we take a more direct approach. Place new corals, anemones, plants or algae in the preferred spot in the display from the very start. Atop the aquarium cover, or upon improvised support such as PVC rods, place a stack of plastic screen or hardware clothe (bulk flyscreen used for windows or doors) cut in squares that are slightly larger than the footprint of the new organism that we are acclimating. About a dozen sheets will be enough. In the shadow of this screen, the new coral can adjust very gently to new lighting by the removal of a single sheet of screen every other day or so for a couple of weeks until all sheets have been removed. Any concerns about deficiencies in light can possibly be allayed with regular feedings or other provisions (refugia, adequate dissolved organics, sand stirring, etc.) for our filter feeders. There are indeed many other novel ways of acclimating corals worthy of a separate discussion altogether. A gentle acclimation is particularly important for recently imported corals. Although they may have come from a place on the reef with sunlight much brighter than your artificial lamps, the extended time in holding and transit in dim light or darkness from the point of collection to the final destination (your merchant's tank or your home aquarium) was likely a week or more. Light shock is often the final insult to stressed and "road weary" corals. New corals need to be handled conservatively and a gradual acclimation to bright reef lights is always a safe approach.

These suggestions and thoughts presented here are but one man's perspective. If I have given you pause to reconsider habits and husbandry, or relieved some anxiety you may have had over the expensive and important components of lighting for your reef aquaria, then I have succeeded. Best of luck to you in all of your endeavors, Anthony Calfo.

If you have any questions about this article, please visit my author forum on Reef Central.

Reefkeeping Magazine™ Reef Central, LLC-Copyright © 2008

Thoughts on Reef Aquarium Lighting… Keep Your Eye on the Prize! by Anthony Calfo-