In the age of LED lighting, aquarium lighting has become somewhat confusing or simply more complicated compared to days past. Gone are the days in which you can buy a light, plug it into a simple timer, and be done with it.

That being said, LED lights found over aquariums today give far more control and usability to tank owners, they are super economical and can last much longer than the technology of days past such as fluorescent and metal halide. LED light also acts much differently (in a few ways) and must be set up properly in order for it to work over a reef aquarium.

First, let's get through the common terms and things you need to know to have a basic understanding of modern aquarium lighting. After that, we can move on to choosing the right light fixture for your tank and finally how to set it all up in subsequent lighting episodes.

Light Spread

Watch Video: Master Spread - The Secret to Mimicking the Sun and Sky with Your Reef Tank Lighting

Spread

This is how light is distributed throughout the tank; the amount of surface area the light covers. Think of a flashlight, the light spread is very tight and concentrated right at the lens of the light, that light "spreads out" into a much wider circle of light, covering a much larger area as you move farther away from the lens. 

As it pertains to an aquarium, the further you move an aquarium light away from our tank, the larger spread you will get.  LED lights also have lenses that affect their particular light spread, some are built for a narrow spread and others are built for a wider spread. 

The type of LED or light you are using matters too. Panel style LED fixtures, LED strip lights and T5 Fluorescent lights create a wide, even spread of light. Pendant style LEDs, on the other hand, use a COB or "chips on board" style LED which houses multiple LED diodes on a single chip. This creates a single, concentrated high-power light source. Those pendants then rely upon mounting height and lenses to bend that intense light and create the ideal spread. 

Light spectrum spectrometer

Watch Video: Master Spectrum - It’s time to change the way we think about reef tank LED lighting

Spectrum

Light Spectrum - ROYGBIV: red, orange, yellow, green, blue, indigo, violet. The color of the light. Spectrum matters for two reasons, the spectrum affects the way your tank looks but is also critical for the health of your coral. Corals require a particular spectrum of light to photosynthesis and survive.

Required PAR for corals

PAR

Scientifically, PAR stands for Photosynthetic Active Radiation. It is a measurement of light intensity within the visible light spectrum (400nm - 700nm). We use PAR measurements to gauge how strong the lights are and ensure we are providing enough light for our corals. Corals have specific requirements for PAR and measuring that within your tank will allow you to tune your light appropriately to provide the right conditions. 

Watch Video: Stop killing corals with these simple steps! How to Master PAR and keep your corals alive for years

Photoperiod

The amount of time each day the lights are ON over your tank. Moonlight doesn't count here, this only pertains to how long the lights are ON, promoting photosynthesis in the tank. Corals require that natural light cycle or "photoperiod" to survive in your tank.

Naturally, the sun is most intense for about 6-8 hours per day which is what we mimic over a reef tank.  We add an additional 1-2 hour ramp-up and ramp-down time on each end to mimic sunrise and sunset to create that effect. There is some wiggle room in the exact length of time and how you ramp the lights but for all intents and purposes, this is a reef tank's photoperiod.

PAR Meters
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  2. SQ-520 Full Spectrum Smart Quantum LED PAR Sensor - Apogee
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    SQ-520 Full Spectrum Smart Quantum LED PAR Sensor - Apogee
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  3. Sensor Wand for PAR Sensors
    Apogee
    Sensor Wand for PAR Sensors - Apogee
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  4. Apogee USB PAR Meter
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    USB Smart Quantum SQ-420 PAR Sensor - Apogee
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  5. Seneye Reef Monitor
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    Seneye Reef Monitor
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  6. Seneye Reef Pack With WiFi Web Server
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    Seneye Reef Pack With WiFi Web Server
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Wattage

Before LED lighting, you could choose a fluorescent or metal halide light based on watts per gallon. Unfortunately, this rule no longer applies because 100 watts of Fluorescent lighting will not produce the same output as 100 watts of LED lighting. That said, you can compare the strength of lights with each other so long as you stick to the same lighting technology. 

For example, a 100 watt LED is going to produce just about twice as much light when compared to a 50 watt LED light. A 150-watt metal halide will not be as strong as a 400-watt metal halide.

So wattage is not used to choose the light fixture directly rather it is used to compare various options within that particular style or type of lighting. When it comes to choosing an LED light, just choose a light made for your particular tank size and shape. Manufacturers advertise these specifications and you should also check out our Buyer's Guide To LED Lighting for more detailed information.

Shimmer

Shimmer happens when the light reflects and passes through the water's surface creating different shadows.  When the water surface is moving, the shimmer lines move along with it. Single point source lights create a much stronger shimmer compared to a wide panel or spread-out light sources.  Pendant-style LEDs and metal halide lamps create the most significant shimmer in an aquarium which is then amplified with surface water movement.

EcoTech Marine XR15

Mounting Height

How high off the water's surface you mount the light.  Mounting height will not affect spectrum but will affect spread and PAR (intensity).  The farther away from the water you get, the spread will get larger and the measurable PAR will decrease.  

Aquarium lights are designed to have optimal mounting heights and will include a recommendation - "Mount the light 8-12" from the water's surface". This is also something we test internally during our BRStv Investigates lighting experiments by observing how much light is lost as we move the light up and away from the aquarium. The goal within our tests is to get the maximum light spread without losing more than 15% of the output over the edges of the tank. 

Lighting controls for Aqua Illumination

Control

There are varying levels of control you can get with an aquarium light.  Classically, aquarium lights didn't even have an on/off switch, they simply turned ON when you plug them in. Fast forward and Fluorescent T5 lights started to include on/off rocker switches, inline dimmers, and even digital timers built right it in.  

Enter the world of LED lighting and controls have become far more advanced with spectrum and intensity control, an internal timer, and even special effects like "acclimation mode". Some LEDs have digital controls built right into the fixture while others offer App control via your Smartphone. WiFi or Bluetooth technology is used to communicate between your device and your light fixture, you can then interact with the light fixture via an app which really adds a whole new layer of accessibility to these advanced light control capabilities.