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Lighting Your Marine Invertebrates:

Reef Lighting Without Controversy!

by Anthony Calfo

A PA super reef set-up

Popular debates over so-called "best" reef lighting schemes for marine invertebrates are ever so much ado about nothing. Yet if you get enough beers into the wrong group of aquarists debating the issue you are likely to instigate a riot the likes of which you'll not find outside of a good football match! The address of lighting symbiotic invertebrates may be the single most important issue of captive reef husbandry and does indeed warrant thoughtful consideration. Unfortunately, many aquarists are distracted by ancillary and even erroneous issues that are either mere amplified products of myth or advertising legend. While lighting technologies are evolving at an exciting pace, with assuredly some to many benefits for aquarists, there are tried and true applications that will admirably serve the marine aquarist that cares little for the bulk of the debate about numerous competing lamps and fixtures.

It is my intent with this article to distill the methodologies commonly applied in lighting symbiotic invertebrates into a concept that will lend my fellow aquarists a simple and reliable ingredient for success in reef husbandry. If you are the type of aquarist that will be satisfied by expending 10% of your resources to gain 95% efficacy…read on, my friend! On the contrary… if you are that rare exception of an aquarist that needs or seeks the last 5% of performance from a system dynamic and are willing to spend a lot of your resources to do it… please pause for a moment and reflect. Better yet… stop and put down the iron bar that you were using to pry the last of that communion money you were saving from your wallet to buy an expensive lighting system. It is not natural, normal or even necessary to spend as much on reef aquarium lighting as one would on a small automobile. Indeed, the whole issue of reef lighting is inflated and imposes an extraordinary amount of stress and expense upon too many aquarists.

The two most common questions posed by contemplating aquarists on this topic are, "How much light do I need," and, "What are the best kinds of bulbs?" These questions are fair and quite natural to ask but unfortunately they open the door for misinformation and ill-advised counsel. Without knowing which specific symbiotic invertebrates are being kept, any answer to the above questions is like putting the cart before the horse, so to speak. It is crucial for an aquarist to take inventory of the invertebrates that they have or intend to keep and then evaluate the animals' individual needs. Only then can we find a suitable lighting scheme that will help them to hopefully exceed their compensation points for photosynthesis (the minimum amount of radiation needed for their endosymbiotic zooxanthellae to generate enough oxygen for carbon dioxide to be produced during respiration). At the compensation point, however, a coral may only survive with just enough food from photosynthesis to maintain vital functions, but has little or no resources in surplus for growth or reproduction. Aquarists with corals that seem to live "forever" but don't seem to grow much or at all should consider increasing light and/or feeding levels gradually. They may actually be holding their corals too close to the compensation point. Indeed, many corals kept inappropriately under modest illumination can ultimately thrive, grow and reproduce if supplied with food to compensate for the deficiency in available carbon from weak photosynthetic activity.

The topic of feeding corals, however, is another matter of great significance. Rest assured though that most every coral requires at least some feeding, and most should be fed several times weekly if not small amounts daily. How they procure their meals and by what method varies by species. Some corals feed organismally (zoo- and phytoplankton "particles"), others feed on a much smaller scale (mucus, floc, bacteria, etc.) and still others by absorption. Most feed by some combination of these feeding strategies. Yet few, if any, popular coral are entirely autotrophic (able to harvest all necessary elements from the products of photosynthetic activity alone). Although much work needs to be done regarding coral nutrition, enough anecdotal evidence and intelligent consensus on the matter in aquariology exists to give an aquarist a good foundation upon which build, learn and grow in reef animal husbandry.

Beyond the compensation point, aquarists may aspire to illuminate corals up to their saturation point. The saturation point in essence is the point at which any extra radiation will not improve photosynthetic productivity. The zooxanthellae reach the limit of their ability to produce oxygen and subsequently the amount of carbon that can be "fed" translocated to the host. As aquarists, it is not easily possible to test or evaluate the level of photosynthetic activity for any coral. In fact, even if we could know that we are reaching the saturation point for a given specimen… that likely leaves all of the many other species in the tank at various levels of satisfaction regarding their respective saturation points. This dilemma illuminates one of the most underrated problems with modern reef keeping: the reality of garden reef aquaria.

What I mean by "garden reef aquaria" is the popular application of mixing reef invertebrates from the widest spectrum of locations on a reef. Scleractinians (e.g. hard corals), octocorals (soft corals), zoanthids, mushrooms, sea fans, hamsters and Smurfs are all commonly thrown together under one standardized lighting outfit (OK… at least most of the aforementioned creatures are mixed together: not everybody has gorgonians). With due consideration for the fact that mushroom/false-corals  (corallimorphs) collected at 20 meters are less likely to thrive in the same aquarium next to a yellow leather coral (Sarcophyton elegans) collected in ankle deep water, one is faced with a challenge. We can either accept the fact that one or both will suffer for the unnatural mix under standardized lighting, or we can resist the temptation to mix them at all and separate them to species-specific displays. Unfortunately neither is likely. Most aquarists do not relish the former notion of a beautiful animal suffering and dying in their charge. Alas, most aquarists are also not likely to resist the temptation to mix many different animals awaiting purchase in a tantalizing shop display! So… can the mixed garden reef display even be sanctioned and supported? Actually, the answer is yes.

I now favor displays of reef invertebrates that are grouped by family, species or region/niche, however it was not always so. Early on as an aquarist, I too assembled my collections rather whimsically or with a strong emphasis on aesthetics (the mixed garden reef aquarium). Whatever one's motivation for mixing unnatural reef invertebrates is, reconciliation may be possible. The key is to illuminate the display adequately but not to over illuminate it. In effect, we are trying to find the lowest common denominator for reaching the compensation point for all of our charges without exceeding the saturation point for some (as the case might be for example with an adequately illuminated shallow water "Yellow Leather" coral next to an over illuminated deep water zoantharian). Excessive illumination (photoinhibition) has become a more prevalent problem in reef keeping with the increased popularity of aquarists trying to make molten lava in their aquariums via banks of 400-watt metal halides suspended over soft corals in less than 50cm of water. Such corals shocked by photoinhibition often pale in color ("bleaching" or expelling their pigmenting dinoflagellates and any remaining zooxanthellae shut down, effectively leaving the symbiotic host to starve to death. With a more tempered lighting scheme, various corals can be targeted for specific feeding to spur growth and reproduction in the absence of light far above the compensation point. Since it would be impossible to optimally radiate a reef aquarium that included anything short of a same species mix, the address of extra and targeted feedings is inevitable and appropriate to insure a thriving population of reef invertebrates (and it will likely save an aquarist a significant amount of money on luminary hardware and operation too).

Perhaps an even better compromise is flexibility on the nature and species of invertebrates kept. With so many wonderful species of reef invertebrates to choose from, I generally advise aquarists to collect a more compatible selection of animals with regard for like husbandry preferences. One might try to replicate a low tide environment with predominantly high light Acroporids and Pocilloporids (the infamous S.P.S tank: so-called Small Polyped Stony corals). Another exciting display might include lagoon species of soft corals or free-living scleractinians (like the Fungiids) on the sand bottom. And even less common but very dramatic displays represent the "twilight" denizens of deeper water (aposymbiotic / non-photosynthetic) and wild colored corals, shy big-eyed fishes, and fascinating sessile invertebrates). Each microcosm can be maintained with less effort and assumedly more enjoyment for the aquarist by assembling animals from niches with like physical requirements of light, water movement and composition.

With a bead on the needs of your collection (low light, moderate light, high light), the decision between standard fluorescent, VHO or power compact lamps, and metal halides is hardly as difficult as it might appear. For some clarification on the above categorization, let me give some examples with the understanding that there are often exceptions within a family, but the advice given represents the majority (trying to serve the greater good). Low light creatures include quite a few zoantharians and so-called L.P.S. corals (Large Polyped Stony corals). Many of these are collected below 15 meters with some found beyond 30 meters! A few examples include many corallimorphs (mushroom false-corals), "Large Button" polyps like Protopalythoa grandis, Duncanopsammia, and even most of the Catalaphyllia "Elegance" corals collected today (some of these purple-tipped beauties are found in near darkness at almost 30 meters (as an approximate value, the light at this depth is close to just 1% of surface) and suffer from light shock on import under bright lamps… indeed significant if not the primary catalyst in the recent plague of difficulties with this genus). Moderate light corals include many of the popular octocorals kept like the soft corals families of Alcyoniids and Neptheids. Far and away, corals in this category are some of the hardiest and most forgiving for many reasons, not the least of which is their compatibility with commonly under-illuminated aquaria (often fluorescent lit systems). High light invertebrates include many of the S.P.S corals like Acroporids and Pocilloporids, and most Tridacnid clams. Use these guidelines loosely and know that it is best, of course, to research the needs of each animal at least by genus and better by species whenever possible.

Once we can categorize the mix of corals and their subsequent needs, we look to the various lamps and outfits to achieve our luminary target. At this point an aquarist might feel overwhelmed by the plethora of lamp types, styles and wattages. If I hear one more aquarium light manufactures tout yet another watt-per-gallon "rule of thumb" for reef invertebrates, I think I shall laugh myself to incontinence. For any such rule to be remotely useful, one must know the depth of water illuminated, the needs of the species being kept and the limits of a given lamp over that range. It is antiquated, inaccurate and potentially dangerous for anyone to offer such a "rule of thumb" on wattage to an aquarium gardener. I may never see what lighting recommendations defined by wattage can do for animals that run the gamut from those living off of the reflected light from a bowed, bald head reading a newspaper to others that should nearly be taped to the powered lamp for their demand for radiation. 

It is obvious that fundamentally a watt-per-gallon rule is worthless when comparing the mechanics and ability of very different lamps to penetrate the dense medium of water at depth. 175 watts of standard fluorescent light appears dramatically different than 175 watts of metal halide illumination at 50 cm of water. Even different makes, models of the same sort of lighting gear produce different intensities and spectra. A submersible light meter makes this contrast starkly clear. Many symbiotic animals under the metal halide lamps at such depth will do very fine while nearly as many of the same invertebrates will struggle to reach their compensation point of photosynthesis if they even can at all under standard fluorescent tubes. Does that mean the metal halides are better: not necessarily. An aquarist must simply match the needs of symbiotic invertebrates with the "best" lamp at the water depth for said specimens in residence.

At the risk of this article seeming anticlimactic, we must concede that there is no such thing as one "best" reef lighting scheme. I will, however, go on record by sharing my own personal observations and preferences. For the benefit of readers unfamiliar with my work, let me offer my credentials. I have been an aquarium industry professional for the last decade working at most levels in the chain of custody for marine fish and invertebrates. I was an early participant in the mariculture of reef coral and invertebrates, operating a greenhouse with 30,000 liters of seawater for coral propagation (animals cultured for ornamental and zoological organizations). I am also the author of the Book of Coral Propagation, Volume 1 (450 pp). [The second volume of my work on coral propagation will be released in 2003 with the first of three volumes of the Natural Marine Aquarium series co-authored with Robert Fenner (Conscientious Marine Aquarist) and Steven Pro of Wet Web Media.] And so, without further ado let me offer the following guidelines.

Sidebar (added title): Types of Lighting, Application

* HQI and Metal Halide Lamps (MH):  

They provide very good to excellent penetration/delivery of useful light at depth. They are arguably necessary for aquaria 60 cm. water depth and deeper over symbiotic reef invertebrates.

Quality lamps in the 6500K to 10,000K color range generally issue the best rated light (PAR) for symbiotic invertebrates. Supplementation with actinic (blue) light is not even necessary with such bulbs (they have enough blue spectrum). MH and HQI lamp colors above 10K have more blue wavelength than necessary for mixed garden reef aquaria. Aqualine Buschke, Iwasaki and Ushio (alphabetical listing) have categorically performed very well in independent product tests.

They (MHs and HQI) are the most cost effective illumination for aquaria among all lamps when one considers lamp life (2-4 years), they have a strong tendency for bulb colors to stay true (useful longer throughout life of lamp), and they are most cost effective to operate (more useful PAR per watt than any other lamp style).

The heat generated by these and any high intensity lamps are easily tempered with properly designed canopies or pendants for fixtures. Marketing and advertising that criticizes HQI and MH units for shedding excessive heat conveniently overlooks similar heat produced by other high intensity lamps (like VHO and PC). All such arguments are moot in a properly ventilated system.

Glitter lines produced from refracted light is theorized to be very stimulating to many reef invertebrates under these lamps. Fluorescent lamps do not produce this aesthetically attractive dappling of light.

Mount lamps 15 to 35 cm above water surface.

BEST BETS under HQI and MH lighting… Clams, cultured invertebrates (faster growth of many Alcyoniids, symbiotic Gorgoniids and other soft coral), shallow water scleractinians like Mussids, Faviids, Acroporids, Pocilloporids and Poritids.

* High Intensity Fluorescent Lamps (VHO and Power Compact/PC)

Fluorescent lamps by comparison are available in the widest range of colors, shapes, and sizes. They are truly the most flexible luminary hardware for any installation.

Aesthetically, fluorescent lamps can produce some of the most attractive spectra of light over reef invertebrates. They are ideal for viewing and photography. Actinic blue light showcases the iridescent pigmentation of many reef invertebrates and adds to their vitality.

High intensity fluorescents are recommended for medium to high light invertebrates in aquaria up to 60cm water depth.

Most fluorescent lamps have a short useful life of 6-10 months for optimum growth of coral.

Some fixtures are significantly less expensive to purchase compared to HQI and MH systems. Thus, they serve a crucial role in the aquarium industry for helping aquarists afford to enter the market segment of reef keeping. Inexpensive and effective systems are even quite possible to assemble with DIY store available white daylight tubes (growing coral well for considerably less money than designer lamps… check for bulb colors near 7000K).

Mount fluorescent lamps no further than 15 cm above the surface of the water. Close to 7 cm may be ideal. 

Daylight colored tubes (near 7,000K) are ideal for shallow water and high light species, while increasing amounts of blue actinic light are appropriate for deeper water species. A 50/50 split of white daylight and blue actinic light will often satisfy low to medium light demanding invertebrates. Categorically, corals acclimated to high intensity fluorescent lighting at a ratio of 3:1 tubes (daylight:actinic) fair very well.

BEST BETS under VHO and PC lighting 

Most octocorals, many scleractinians, most zoantharians. An excellent all purpose light for reef invertebrates in 40 to 60 cm of aquarium water (3:1 favoring daylight).

* Standard Output Fluorescent lighting (SO or NO)…

The same general attributes as per above for high intensity fluorescent tubes with the limitation of its potential to support symbiotic invertebrates at depth.

Recommended only for the least demanding animals in shallow aquaria 40 cm or less in depth.

Mount SO or NO lamps 7-10cm above water surface

*Questions for the author or about the Book of Coral Propagation may be sent via e-mail to anthonycalfo@readingtrees.com or navigated through www.readingtrees.com or www.wetwebmedia.com

With kind regards, Anthony Rosario Calfo

Small Marine Aquariums
Book 2: Invertebrates, Algae
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by Robert (Bob) Fenner
Small Marine Aquariums
ook 2: Fishes
New Print and eBook on Amazon: by Robert (Bob) Fenner
Small Marine Aquariums Book 3: Systems
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