Illuminating Reef Tank – Reef Tank Lighting Guide for Beginners.

There’s no denying the power of light. From warming our planet to growing our food, life itself wouldn’t exist without the illuminating gift of sunlight.

Few hobbies amplify the complex world of light to the degree as reef tanks. As many novice reefers realize, lighting is far more than an aesthetic design. This doesn’t mean you can’t appease your visual style with appropriate lighting. In fact, light design is among the most pleasurable elements of any tank setup.

However, lighting your reef tank isn’t as easy as popping into a hardware store and buying a 4-pack of bulbs.

Unless you’re working with an established reefer, diving into the bright world of tank lighting can feel as blinding as trying to count sun spots. As a beginner, the first introduction to reef tank care is a whirlwind of terminology, parameters and topics. It’s no wonder far more people abandon their dream of owning a slice of the ocean than see their watery fantasies realized.

I’m not here to sugar-coat the facts. Adapting to the mysterious underwater rules of saltwater aquariums is a challenge. But, thankfully, it’s not as complex and difficult as you may think.

Much like learning any new hobby, the first step is knowledge. Unlike the countless others who’ll never experience the joy and wonderment of a reef tank, you have a special weapon: us.

With decades of combined experience, the entire ReefHacks team is here to support your watery journey. Although there will be times when this hobby feels confusing, you can always turn to our resources for straightforward answers.

Now, let’s spark the bulb of understanding and put on our sunglasses as we jump into the brightly colored topic of reef tank lighting (sunscreen not included).

The Ease of Enlightenment - Light Spectrum Defined.

Think all light is the same? While our eyes perceive light intensity and color uniquely based on the number of Rods and Cones, the usable spectrum of light also varies depending on the photosynthetic organisms you intend to focus on. Understanding the visible and invisible qualities of light is the cornerstone of building a healthy reef tank.

When I refer to “spectrum,” I am not discussing the color, or hue, of light. I am referring to the spectral composition itself which includes all wavelengths of light produced by the source.

Keep this in mind. Light spectrum = total spectral composition of the source itself. Color = light as perceived by the human eye. This may help clarify topics when these terms are used interchangeably.

Before getting into the specific light spectrum wavelengths, and its impact on coral, let’s briefly discuss why light is important.

An Ancient Collaboration Between Plant and Animal.

I’m sure you remember learning about photosynthesis in science class. Essentially, this is when plants use sunlight to make their own food.

“Wait! Aren’t coral animals? Why are you talking about photosynthesis? I’m confused!”

This is a paraphrased quote I’ve heard countless times when teaching novice reefers about coral lighting. Here’s my response, “Yes!”

Okay, that’s not very clear. Let me explain further. Officially, corals are animals as they can’t make their own food. As you already know, only plants do this. Rather than create their own food via photosynthesis, corals sweep food out of the water with their tentacle-like branches.

Here’s another fact that may surprise you. What we know as corals are actually communities of hundreds of thousands of creatures known as polyps. These soft-bodied critters lay the foundation of coral reefs as they secrete calcium carbonate, or limestone.

So, if corals are actually animals, why are we discussing photosynthesis? Because, like many oceanic organisms, corals aren’t a single organism type, but rather, a cluster of organisms working as partners.

Living inside coral tissue is an alga known as zooxanthellae, which in many cases, is very much a plant. This microscopic algae and coral benefit each other.

The algae uses coral metabolic waste to support its photosynthesis while the coral uses the oxygen produced by algae photosynthesis.

Essentially, what we see as a uniform coral reef is actually an ancient collaboration between plant and animal. While this alga supports the health of coral, it’s also responsible for the vibrant and unique colors that make coral so desirable.

Because of this intimate relationship, reefers must treat coral as both plant and animal. This is one reason why lighting is imperative.

Now that we’ve covered this fundamental topic, let’s return to our investigation of the light spectrum.

The Many Colors of Light - Spectrum and Coral.

Do you feel light color is simply an aesthetic choice? If so, then you’re only half-right.

Color, or its position among the light spectrum, is a major component of the photosynthetic process. Zooxanthellae, which is the algae living within coral tissue, doesn’t absorb light uniformly. Certain wavelengths of light are absorbed more efficiently than others.

As you may already know, chlorophyll plays an integral role in photosynthesis. The majority of coral feature Chlorophyll A, which features an affinity with two light spectrums:

• Violet Light - 440 nm wavelength.
• Red Light - 675 nm wavelength.

Of course, this doesn’t mean a reef tank can only thrive with shades of red and violet within this specific nm reading. There are other compounds, such as carotenoids and Chlorophyll C, which respond to other wavelengths of light. This information should be used as a baseline saltwater aquarium lighting guide, not regarded as the final say in reef lighting.

The spectra of light produces three wavelengths, which include:

• UVA - This is the visible light spectrum, which is paramount for photosynthesis. The actinic, or light capable of producing photochemical reactions, measures bellow 400 nm, and is the spectrum most important for marine organisms.
  • Warm Light Colors - Yellow, Orange and Red.
  • Cool Light Colors - Blues and Greens .
• UVB - Classified as invisible light, this is the wavelength responsible for burning your skin while enjoying the summer sun. 
• UVC - Have you ever heard of ultraviolet sterilization? This light wavelength actually kills bacteria and is dangerous, and even deadly, to animals.

Light wavelength also determines how effectively it can penetrate water. Certain wavelengths, such as red, orange and yellow, are more readily absorbed. On the other hand, blues and greens dive deeper into water and play an essential role in coral algae photosynthesis.

The Lingo of Light - Reef Tank Lighting Terminology.

As with any hobby, there’s quite a few terms you’ll come across that are unique to reefing. While you’ll naturally absorb this information as you progress, let’s take a moment and review several essential lighting terms.

Kelvin Rating | Abbreviation: K

This term defines the color of light as perceived by the human eye. Aquarium lightbulbs generally feature ratings based upon this unit of measurement. Here’s the most simplistic way to identify Kelvin values:

• Higher Values = Bluer Light.
• Lower Values = Warmer Light.

For reef tanks, higher Kelvin bulbs are typically used as blue light penetrates water better than other hues. As an added perk, blue light tends to reduce nuisance algae growth and is regarded as an aesthetically pleasing color hue. However, it’s been noted that lower Kelvin bulbs with a rating around 6500K tend to promote faster coral growth, but aren’t as visually attractive.

Nanometer Rating | Abbreviation: nm

Nanometers are used to measure extremely small lengths, which makes it ideal to measure light wavelengths. Visible light measures from 400 - 800 nm. As you dive into the lower measurements below 400 nm, you enter the world of UV light while measurements above 800 nm belong to Infrared (IR) light.

Nanometer ratings are beneficial for determining the effect of a specific wavelength on a surrounding environment. This is important when tending to coral as each species prefers a specific wavelength. We’ll discuss measuring tank lighting in the PAR definition.

PAR Rating | Abbreviation: PAR

PAR, or Photosynthetically Active Radiation, is a common method of measuring light in our hobby. Measurements are used to determine intensity (Quantum Flux) at specific points throughout the aquarium.

As mentioned earlier, zooxanthellae algae thrive when exposed to specific wavelengths of light. Achieving ideal PAR values based upon coral species requires more than a keen sensitivity to light. In fact, meeting these values without specialized equipment is almost impossible due to our inability to see the full light spectrum.

While there’s several excellent PAR meters, we use the Seneye REEF metering system (Read The Full Review Here), which elevated our accuracy and control. You can find this meter online, and in most cases. Or you can even rent an Apogee PAR meter at your local fish store or reef club.

What’s the ideal PAR reading? Well, like many elements in this hobby, that answer is tricky. We prefer to keep our PAR around 250 to 400 nm, which produces beautiful coral growth and coloration.

Here are the PAR readings map for our Red Sea REEFER 170 tank. The 24" ATI Sunpower 8 bulbs fixture is 8 inches over the water surface:

The Bulb Breakdown - Exposing Beauty and Health.

Now that we’ve covered essential terminology and background information, let’s move into the real world application.

I remember a novice reefer explaining his first introduction to tank lighting. There he was, standing in his fish shop staring at the endless array of lightbulbs. Each product proclaimed its perfection with conviction.

Frustrated, he bought the fixture suggested by the unfortunately uninformed clerk. I’m sure you can guess what he experienced after installing the lights. His coral growth and vibrancy didn’t meet its health and visual potential.

While coral may grow and stay alive in many lighting situations, our goal isn’t simply to keep these beautiful organisms living. Our goal is to allow each tank inhabitant to thrive and achieve its full potential. Even though lighting is only one ingredient, it’s among the most impactful.

Essentially, there are four primary lighting fixture types designed for reef aquariums. As with all components, each offers specific advantages and disadvantages. However, when it comes to ease, effectiveness and operating function, there’s a stark difference between each bulb type.

Metal Halide - The Traditional Choice Isn’t Always Best.

Typically used in commercial tank setups, metal halide lights are classified as a high intensity discharge, or HID, system. The light source is an internal bulb usually protected by an outer glass casing. When activated, electricity flows through an arc tube and causes a reaction with the tube-encased metal salts and gases to emit light.

The primary benefit of metal halide lighting fixtures is its light intensity. A single fixture can produce hundreds of watts of energy, which means fewer bulbs are needed to reach high illumination. Recommended wattage varies based on aquarium depth. For example:

• 175 Watts is used for 20-inch deep tanks with SPS or mixed-type corals and clams.
  
• 250 Watts is used for 30-inch deep tanks with SPS or mixed-type corals.
  
• 400 Watts is used for 48-inch deep tanks or a tank featuring dedicated SPS corals.

While metal halide fixtures aren’t rare in consumer-level hobbyist setups, their power and other features makes it more suitable for commercial coral propagation.

So, what’s the main drawback of this fixture? Metal Halide lights can run hot, which can elevate room temperature in certain situations which can also increase water temperature. While purchasing a chiller is an option, this can add to the expense and complication of your setup.

LED Lighting - Maximum Flexibility, Control and Functionality.

The latest craze in reef tank lighting is also the most advanced option. By now, you’re likely familiar with the various benefits of LED lights. These advanced light sources offer an incredible amount of light without reaching the scorching temperatures of metal halide fixtures.

When compared to metal halide bulbs, LEDs are preferred as they don’t transmit heat into your tank water. However, don’t take this as a sign that they don’t produce heat. Rather than sending heat downward, LEDs generate and transmit heat upward. If left unchecked, heat generation can reduce LED chip lifespan. Circumvent premature LED death via ample air circulation or with a cooling fan if installed in an all-in-one hood or canopy.

So what is best LED lighting for reef tank?

T5 Lighting Fixtures - Stability, Power and Effective.

T5 reef lighting fixtures have been on the market for quite some time. What I appreciate about T5 lights is its ease. Unlike LED lights, which aren’t extremely complex but require previous knowledge to achieve ideal lighting hue and reef tank lighting schedule, T5 fixtures are a breeze to operate.

As with LEDs, T5 fixtures operate at a lower temperature and come in a variety of sizes. The most important element is simply choosing the best bulb combination for your specific tank.

Hybrid Lights - The Brilliance of Multiple Light Sources.

While the aforementioned fixtures offer their own benefits, none deliver such illuminating power as hybrid reef tank lights. As you browse different lighting options and review commentary on reefer forums, you’ll quickly see hybrid models are in-demand.

Essentially, this fixture combines LED and T5 bulbs. I consider this the best of both worlds. You receive the precision and spectra flexibility of T5 bulbs with the efficiency and control of LED fixtures. As a beginner, the power and user-friendliness of hybrid fixtures is worth investigating.

Lighting Cycle - Replicating Nature for Vibrant Growth.

In brief, a lighting cycle refers to how long you should illuminate a tank. Remember, the underlying purpose of a reef tank is to replicate oceanic conditions. While it’s impossible to perfectly reproduce life in the ocean, with a little trial-and-error, you’ll find a reef tank lighting schedule that works best.

To better explain this topic, I’ll use our tank as an example. We use the ATI SunPower T5 eight-bulb lighting fixture as well as the Reef Brite Tech of Actinic color. This configuration is similar to what you’d find in a hybrid fixture setup.

If you wish to use a hybrid design, we recommend the ATI Hybrid fixture. However, you can also follow our lighting scheme for similar results.

Here is our daily 12 hours lighting cycle:

• Morning Cycle - We run the 2 T5 Actinic bulbs and the ReefBrite LED for two hours. 
• Daytime Cycle – Then for eight hours, we turn on all 8 T5 bulbs and the ReefBrite LED.
• Evening Cycle - At the end of the day, we use again only the 2 T5 Actinic bulbs and the ReefBrite LED for 2 hours.
• Overnight Cycle - Make sure to turn off all the lights overnight. Never leave any of the lights on, even on minimum settings. Remember, everything needs a little darkness to thrive.

Our reef tank bulbs combo:

• x4 ATI Blue+
• x1 ATI Purple+
• x1 ATI Coral+
• x2 ATI Actinic

Reef Tank Lighting - The Brighter Path to Tank Beauty.

While we’ve covered the essentials of tank lighting, there’s much more to be uncovered. However, using the knowledge covered in this saltwater aquarium lighting guide, you’re on the path to creating a beautiful, healthy and vibrant tank.

As always, we’re here to help. Whether you’re just starting out, or already have a lighting system and need some advice, visit our Facebook page and send us a message. On behalf of the entire Reef Hacks team, welcome to the brighter side of reefing!

P.S: Special thank you to Tullio Dellaquila from ReefBrite for the consultation and edit on the article.

by Yuliya Ivanova for ReefHacks.

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