Feature Article: The Static On Static Lighting: Suggestions For Better Lighting Applications Of Photosynthetic Reef Organisms - Moving Light Systems (MLS)
As if the arena of reef aquarium lighting weren’t complex or daunting enough, let’s contemplate the way that we physically deliver light to symbiotic reef organisms. Beyond rudimentary considerations of lamp type, power and distance off the surface of the water, I mean to convey that for dedicated aquarists with the means and interest to experiment, there are some very interesting concepts for finessing luminary aspects with motion, which are remarkably inexpensive to install. Some advanced aquarists have really begun to experiment in earnest with ingenious notions for putting aquarium lamps in motion (with motorized planar and inclined tracks) to enhance the aesthetic effect, if not improve the health and vigor of captive reef life overall. This article is a simple primer with reminders for fixed lamp applications, suggested improvements for all systems, and an introduction to the featured moving light systems (MLS).
The foundation of the premise for moving light systems is to illuminate photosynthetic organisms in a more natural manner that attempts to replicate the path of the sun in the sky, or to at least radiate subjects at changing and sometimes severe angles that are impossible to achieve otherwise with fixed lamps. One of the most significant practical benefits to such strategies is that fewer lamps are required to illuminate a given surface area (one moving 250 watt metal halide instead of 2 fixed 175 watt lamps over a 24” deep aquarium, for example). This is certainly very appealing news to aquarists eager to save money on the initial purchase and ensuing operational costs of expensive reef light fixtures. From the perspective of husbandry, organisms receive light from more natural and balanced dimensions (and of welcome, variable intensity with each pass), which may be reflected favorably in their growth rates and ultimate morphology.
Admittedly, these applications are not going to improve the success of your display by a scale of considerable magnitude. Elementally, they are not even new concepts at all, as you will read below. But most require little effort or expense to employ, some clearly seem to improve the delivery of light, and all are likely to save money on operational costs. In a hobby full of passionate DIY participants, moving light systems are likely to be welcome candidates for home-engineered technologies that evolve to suit our needs and pursuit for stunning reef displays. Without harnessing the power of the sun (using natural sunlight under skylights, through windows and in greenhouses) we need to constantly review and explore new methodologies that improve artificial light applications for aquaria.
Let’s review some suggestions for better traditional aquarium lighting (fixed) at large before we get into the heart of the matter with moving light systems. Most of the following recommendations presented are well covered in popular legend, if not trade literature or research. Although few of these can be written in stone, most can be taken at face value to serve the greater good, for newer aquarists in particular. Specialists can deviate with judicious experimentation.
The first aspect of mention is simple enough to be obvious, yet is easily forgotten or overlooked. For all light fixtures, keeping the lamps free of dirt and debris is crucial and should be completed as a weekly chore at least. The slightest film of dust or salt creep/spray can markedly reduce the amount of light that actually makes it into the aquarium. Where lenses and glass or acrylic canopies are employed, the same holds true. Any obstruction between the lamp and the water’s surface can be an enormous impediment. It’s ironic to see struggling reef aquariums with magnificent luminary hardware that has simply been ignored (or poorly installed) serving merely as a repository for dust and salt creep. Keep all lamps and lenses squeaky clean and crystal clear for all lighting systems.
Water clarity is another challenge that is pivotal to all lighting applications. System water that is not noticeably discolored to the naked eye may still be tinged enough to reduce the penetration of light measurably. Visibly discolored water is a serious impediment and can become a problem in just a few weeks without treatment or prevention. Aquarists are strongly encouraged to use chemical filtration like activated carbon - weekly, if not full-time. A less frequent or altogether neglected address of water clarity can lead to luminary shock with large water changes or sudden improvement of water clarity otherwise. Properly metered and dispensed ozone (using a redox controller, and carbon on air/water effluents) can also be a tremendous boon to water clarity, and has many other benefits to water quality including improved protein skimmer efficacy, higher oxygen saturation, increased redox, and reduced numbers of pathogenic organisms.
Any general concern about chemical media taking out desirable elements (a common but misguided criticism of carbon and like media) can be dismissed in my opinion; even without it, desirable elements will be extracted by good and bad organisms alike. Should we exclude corals from our reef aquariums because they too take out desirable components from the water? Sarcasm aside, supplementation (via water changes and/or additives) is necessary with or without chemical filtration, and good media removes far more bad elements than desired ones, rest assured.
Distance of Lamps / Intensity
The distance of lamps off the surface of the water is also of great importance and is the subject of some manipulation with MLSs, as you will read below. For most fixtures, it is important to mount lamps duly close to the water surface. The amount of light penetrating the water increases markedly with descent/approach. The dynamic is a ratio of intensity (closer) versus spread (higher), and we wish to strike a balance (always with a good reflector) to maximize this ratio. The ultimate position varies by situation. As you can imagine, an exaggerated tall and narrow tank will benefit from a closer lamp to deliver more intense light that can penetrate deeper. On the contrary, a low, wide and shallow aquarium will require a higher lamp position for a wider spread. For average home aquaria, however, that are less than 30” deep, the following applies:
- Fluorescent lamps generally should not be mounted any higher than 3” (7.5 cm) off the surface of the water.
- Metal halides are to be installed around 9” (22.5 cm) for 175 - 250 watt lamps over 24-30” of water (towards 6” off the surface instead for lower wattages, and as high as 18+” for higher wattages).
These suggestions are very generic, to be sure, and need to be finessed by an aquarist on a case-by-case basis. By comparison, the recommendation on fluorescents is far less flexible due to the limitations of the technology. As guidelines, though, they will put most aquarists, too many with unfortunately popular mixed garden reef aquariums, in a reasonable to very good position on lamp distance.
Some other important reminders for improved delivery of light: lamp age, cooling, and orientation. We have a fairly good idea of the useful lifespan of most lamp types. The technologically fixated can buy PAR meter to measure and monitor the quality of their lamp’s output over time (and all of their friends savvy enough can beg and borrow the meter). The rest of us can be assured that most fluorescents are only good for about 6-10 months. Metal Halides (MH) are rather variable with estimates ranging from 1 year to over 3 years (less commonly). It is true that halides are generally more effective (useful) over the span of their life than fluorescents, with some MH being near or in excess of 90% on par (close to mint) at the time they blink out. That is to say, the rendition of color stays true for a longer period of time with halides than most fluorescent lamps, which stray easily and quickly. Some estimates place popular fluorescent lamps at merely 70% effective near the end of their lifespan.
Lamp cooling is an aspect that we do not have an abundance of practical data on in aquaristic literature. We do know that proper lamp temperature (not too much or too little) is necessary to optimize lamp life and color. The trueness of the lamp (resisting a stray towards a less usable spectrum) is very important for optimal photosynthetic activity. In layman’s terms, simply ventilate the hood or canopy vigorously, but be sure not to blow fans directly onto the lamps. It’s best, instead, to just exhaust air by sucking it out of or away from the fixtures rather than blowing into it.
Lamp orientation is an important and often overlooked aspect of lighting applications. The exact orientation of some lamps is said or known to affect their performance. For some fluorescent tubes, there is a hash mark stamped into the metal end caps of the bulb indicating a recommended position (downward usually) after the pins are locked into place. For others it seems to make no difference. With metal halides, we look to the small emitter tube within the lamp. This little “tube within a tube” has a small nipple on it whose orientation can influence the performance of the bulb. Aquarists seem to feel that “nipples up” [keep the jokes to yourself at this point] is the best position. In some cases, it will visibly affect the color of light to a favorably blue/white range (from warm daylight). Note: you can pry the contact tab inside of the lamp socket (only with the power off and the unit unplugged) if needed to get your lamp to seat firmly in a specific position if desired. It also needs to be mentioned that the physical direction of the lamp on whole can make a significant difference in the spread and focus of light. Vertical (pendant) installations are reserved for deep and narrow coverage (like a spotlight). They focus intense light in a very small area and are arguably not “ideal” (value by coverage) for most home aquariums under 30 inches (75 cm), unless the application and effect is a deliberate preference. For horizontal installations, placement will be strongly influenced by the type and efficiency of the reflector used; many aquarists find that lamps mounted horizontal and perpendicular to the long sides of the display afford the best spread of light. At any rate, always consult the lamp and reflector manufacturers for special instructions on orientation and installation whenever possible.
At last, we come to an address of moving light systems. With consideration of the above aspects (and their application of most here, just the same), we take reef lighting to another level… or rather, other dimensions in space literally as we depart from traditional fixed stations for lamps. For the sake of this primer, we’ll limit the detail of hardware simply to planar (illustration at top of article) and inclined light tracks (see below). Advanced aquarists have and will continue to experiment with numerous interpretations of the method.
Indoor horticulture has long since employed suspended lights on motorized planar tracks. If you have never seen them in operation before, they are really as simple as they sound: a motorized track with gears/pulleys conveys a fastener (hook or chain) with the light fixture suspended. Organisms under the path of the track receive light of variable intensity and angle of delivery as the lamp passes by. Manipulations of the circuit (number of passes and stops if any) and photoperiod - for example, “double-time” with two cycles of light and dark each in a day, which can sometimes stimulate desirable behaviors such as forcing extra reproductive events. This is particularly helpful with species of commercial interest that only have one strict reproductive event annually. Equipment to produce this sort of carriage is relatively simple to construct for the handy DIY (do-it-yourself) aquarist. Ready manufactured products are available just the same from most any large horticultural or greenhouse supply company (and finally some aquarium suppliers).
In the reef aquarium, with moving light emanating from a waxing and waning distance, the variable angles not only directly illuminate lower branches and regions that a fixed lamp could not, but they also refract light off of various substrates (particularly a light colored seafloor) which provides radiance in sometimes otherwise inaccessible areas as it occurs on the natural reef. Some aquarists like to credit this strategy with the reduced decline of health in corals and macroalgae on their lower regions (pale or receding/dying tissue), especially with maturing and overgrown specimens. It certainly seems like a believable argument to me, at least. This is not to say that there are no overgrown tabling Acroporids in the wild, for example, with pale tissue underside (there certainly are!). But, aquarists clearly seem to have a higher incidence of this phenomena with captive corals. A fixed light source is a very likely causative agent (if not the agent) for such ailments. Moving light systems are a possible solution and bring us closer to mirroring the all- encompassing radiance of the sun on a reef as it travels in a wide arc across the sky.
We may fairly speculate that one of the more interesting benefits of a moving light source is the stimulation of symbionts by the distortion or oscillation of the dynamic between the intensity and spread of light from artificial lights in motion. The unwavering static intensity of a fixed lamp, besides being unnatural, is stressful to weak, sick or recovering cnidarians (by light deprivation in transit or zooxanthellae expulsion from duress, e.g.) as with freshly imported specimens. Aquarists have attempted to compensate for the shock of prolonged and sudden/intense exposure to a fixed lamp by starting compromised specimens on the bottom of the tank and working them up higher in the display slowly over a period of weeks (good). Another popular strategy is to place a new specimen in its proper place from the beginning, but with a stack of cut plastic screen the size of the coral’s footprint above it (better) to assist with acclimation. A dozen or more sheets sit on top of the canopy/cover (or a rig) to filter light and cast a focused shadow on the specimen; single sheets are to then be removed every day or every other day over the first couple weeks to facilitate a gradual acclimation to new or bright light. Better still, some aquarists have proposed exposing stressed coral to short durations (“bursts”) from a new lighting scheme that cumulatively amounts to the expected/proper continuous cycle. For example, a desired photoperiod of 8 hours would oscillate between 30 minutes on and 30 minutes off over a 16-hour period to reach the goal. This has been shown to be remarkably helpful for many struggling coral, yet is perhaps only practical for corals acclimated in isolation - away from the display full of established organisms, which are accustomed to a continuous photoperiod. It’s here that a moving light source might also excel for some new acquisitions with the described waxing and waning of light intensity and direction (sparing the need to adjust the system or canopy at the expense of established sun-soakers in the display).
At length, the integration of a planar track system will take up no more space than one already has dedicated for a fixed lamp system. It will reduce the number of lamps required on a given run and subsequently the cost of power to operate the system. Moving lights also make a handsome aesthetic impact if nothing else. There is concern for some manufactured units not engineered for a quiet living with noise from a continuous/charged motor. Short of finding or building a quieter model, bare in mind that the fixture does not have to be in constant motion. Some very inexpensive but “loud” units (typically ignored in a working greenhouse) have been employed in quiet living spaces by putting the motor on a staggered timer. It’s as simple as moving the fixture in brief intervals (seconds/minutes) at X inches per hour with a multi-event (on/off) household timer.
There are in fact numerous variations on the vehicle for moving light systems that suit one’s varying preferences (noise of operation, electric efficiency, etc.). One of my favorite notions suggested to me was a small, economical motor that efficiently leveraged a weight and pulley to negotiate the rise and fall of a fixture on an incline each day. Whew! The possibilities are endless for putting our lights in motion. Aquarists that are also motorheads (automobile enthusiasts) are probably spinning wheels in their heads as we speak thinking of gear ratios for a motorized track. Aquarists that are engineers have perhaps begun to analyze articles and issues of resistance among possibilities. And I have worked myself up a frenzied hunger for chocolate chip cookies. Hmmm… well, we each get stimulated in different ways I suppose. The point is, do keep an open mind. Our entire hobby is still so very young. Theories and methodologies are evolving so fast that the anally retentive aquarists cannot finish their moot arguments on the last controversial topic before the next one comes along.
In parting, I must say (again, as I often do) that the ideas presented here are not written in stone. I am not interested, competent or qualified to run a disciplined scientific investigation to qualify or quantify any theories herein. I am simply impassioned to share the notions, and hopeful that those folks who are qualified and interested will bring hard science to the mettle of reliable practical and anecdotal information, and report to us in time. Many of us look to the esteemed likes of Dana Riddle of Riddle Laboratories and Sanjay Yoshi, for example, for such science. I am but a dedicated hobbyist - privileged to sights and ideas in my travels that I feel obligated to share. I sincerely hope that folks with strict sensibilities and demands for hard science in our relaxed hobby will understand that there is great benefit in open speculation by the novice that incites thought and experimentation. Or at least, an indulgence would be nice.
In shared admiration of the sea,