Most novice and many experienced saltwater aquarists are hesitant to start a reef tank or upgrade their Fish Only or Fish Only with Live Rock tank to a reef tank because they don't understand the lighting requirements of corals and/or they believe the high price of reef tank lighting is out of their reach. Here is a simple explanation of how much lighting you will need for your reef aquarium and light fixture pricing information.
Reef Tank Lighting "Rule of Thumb"
The simple "rule of thumb" explanation of the lighting requirements for corals is: Three and a half (3 1/2) watts of over 6700K lighting for each gallon of tank water for soft corals and four and a half (4 1/2) watts of over 6700K lighting for each gallon of tank water for hard corals. An example would be a 55 gallon tank would require 192.5 watts (55 X 3.5) of light for soft corals or 247.5 watts (55 X 4.5) for hard corals. There are exceptions to the rule of thumb (some coral species require more or less light than their hard or soft brethren), but for the most part, the "rule" is workable.Lighting Types
Fortunately (or unfortunately) there is a variety of lighting types available for today's aquarists to select from. Each type has it's own advantages (size, output, spectrum) and disadvantages (size, heat output, spectrum).
Daylight or Actinic?
Without going into a long winded explanation, accept the fact that corals and other invertebrates (clams, anemones) need light in the 6700K (the light at the equator at noon) to 10000K range. 20000K bulbs are also available and work well for reaching the bottom of deeper reef tanks. Corals will thrive without actinic light, but you may want to add an actinic light to bring out the blue and green colors in your tank.
Fluorescent
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Available in NO (Normal Output), HO (High Output), VHO (Very High Output), Actinic and 50/50 (half Daylight, half Actinic).
Compact Fluorescent Bulbs (CFL)
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Also known as Mini Twist Compact Fluorescent Bulbs, these bulbs are fairly new on the market. CFL's are power efficient, producing much more light in the right spectrum per watt than their incandescent cousins, using the same screw in fixtures. Cool running, efficient and inexpensive, these bulbs may be the reef light of choice for the future. These bulbs are not currently available in aquarium fixtures, but that hasn't been a problem for creative DIYers.
Power Compact (PC) or Compact Fluorescent
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These bulbs provide light in the daylight and actinic blue spectrum range. These bulbs produce twice the light as the same size fluorescent bulbs. Available in 6700K and 10000K.
Metal Halide
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A very efficient light for reef tanks, providing high intensity light in the right spectrum range for reef tanks. Their downside is the amount of heat they produce and their higher cost for fixtures and replacement bulbs.
LED Aquarium Lighting
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While LED lunar lights have been around for a while, LED aquarium lights for reef tanks are just coming on the market. LED lights have several distinct advantages (low power consumption, low heat output and long bulb life). While these lights are expensive, those who have used them are very pleased with their performance.
Light Fixture Size
Determine the size of the area the light fixture will occupy. If you have a tank that is 48" wide by 16" deep, you won't be able to put a 72" light strip on it, but you can put 1 or 2 48" light strips on it. There are even some 36" fixtures which will work for a 48" tank.Example 55g Reef Tank Light Fixture Choices
Let's take a 55g tank as an example to see what will work for reef tank lighting:
- Coralife 48" Aqualight Double Light Strip
- 260 watts
- 4.73 WPG
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- AquaticLife 48"Compact Fluorescent Lunar Light
- 260 watts
- 4.73 WPG
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- Current USA 48" Nova Extreme 4x54W T5HO with 4 Lunar Lights
- 216 watts
- 3.92 WPG
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- Aqualight Pro 48" HQI/Compact Fluorescent/Lunar Light Fixture
- 300 watts
- 5.45 WPG
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- ecoxotic Panorama LEDs
Example 30g Reef Tank Light Fixture Choices
Let's take a 30g tank as an example to see what will work for reef tank lighting:
- Current USA 36" 2x96 watt PowerCompact Dual Satellite Fixture
- Total 192 watts
- 6.4 WPG
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- Current USA 36" Dual Satellite 2 x 96 Watt
- 192 watts
- 6.4 WPG
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- Coralife 36" Aqualight Double Compact Fluorescent Strip Lights
- 192 watts
- 6.4 WPG
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- Current USA 36" PowerCompact Dual Satellite Fixture:
- 192 watts
- 6.4 WPG
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- Current USA 36" Nova Extreme 4x39W T5HO with 3 Lunar Lights
- 156 watts
- 5.2 WPG
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