First understand the basics!The type of livestock you choose to keep will determine what type of lighting you require. Remember! You are now the sun to these creatures! Various corals & invertebrates require different intensity of lighting. We need to be aware of this in order to be successful in our underwater gardening.
The most common guideline to lighting is watts per gallon. 3-5 watts per gallon for soft coral, 5-7 watts per gallon for large polyp stony corals, and 7-10 watts per gallon for stony corals. This guideline does not paint the whole picture. You must also consider the depth of your aquarium. As light passes through the water column, it loses intensity. In order for high quality light to reach the bottom of a deep aquarium, more output (PAR) is needed. To evaluate a lighting source, consider the LUX and PAR of the bulb. What is LUX?
Lumens is the candle power of a light, the higher the lumens, the brighter the bulb. LUX is the term to describe the lumens per sq meter. LUX measures light that we are able to perceive, not what the corals use.
What is PAR?Photosynthetic Active Radiation (PAR) measures the full spectrum and gives the best predictor of light output. PAR is measured in microEinsteins(mE); the sun produces 2000mE. Since we are trying to replicate the effects of the sun in a reef aquarium, our goal is to produce light as close to 2000mE as possible.Common Lighting TechnologyNormal Output FlorescentThis type of lighting is standard with many starter kits and is often the most recognizable with beginner aquarists. These are the least expensive lights to purchase and tubes are available in a wide range of color temperatures. The lighting tubes lose their intensity quickly because they are usually driven by magnetic ballasts and should be replaced every 4-6 months. A 48" tube will emit 40 watts of light, with an average PAR of 230mE. Due to their limited light output and frequent bulb replacement they are not recommended for reef aquariums. They would be a choice for fish only marine and freshwater systems.VHO (Very high output) FlorescentSimilar in design to normal output bulbs, these lights require a higher output ballast to produce higher wattages. A 48" VHO bulb emits 110 watts of light and approx. 1000mE. VHO lighting is well suited to shallow tanks under 20" in depth. They need to be replaced every 6-8 months. Power Compact FlorescentBy passing light through a smaller focal point, PC bulbs are able to penetrate water more effectively. A 36"PC tube emits 96 watts. 4 96w PC bulbs will produce approx. 1100 mE of light. They are effective in aquariums up to 24" deep. They are useful when housing soft corals and large polyp stony corals (and some small polyp stony corals). PC bulbs should be replaced every 10-12 months. PC bulbs produce more heat than VHO bulbs, so proper ventilation is important. T5 High Output FlorescentThese fluorescent tubes are much smaller than normal output bulbs, but pack more punch. T5 bulbs measure only 3/8" in diameter, so they are easy to incorporate into any fixture as a supplemental light source or can be used as the main lighting in shallow (less than 30"H) tanks when used with proper reflectors. A 48" T5 tube emits 54 watts with significant lumen output & higher PAR value than normal output or PC fluorescent bulbs. T5 lighting will be suitable for any type of coral you wish to keep but those with higher lighting demands may require a system with more bulbs. New VHO T5 lighting systems are now available that will produce the same lighting levels as 250w metal halides without as much heat transferred to the water.Metal Halide LightingMetal Halide lighting is considered the best option for a larger or very demanding reef aquarium. It is also the only bulb that gives you that "dancing sun beam" effect that is so captivating. The bulbs are available in 2 styles: Mogul Base (screw in) or HQI Double Ended.
Mogul based bulbs are readily available in 150, 175, 250, 400, and 1000 watts. HQI Double Ended Bulbs are readily available in 150, 250 and now 400 watts.
Match the wattage of your bulb to the depth of your tank. 150-175 watts for up to 24", 250 watts for up to 30", 400 watts for up to 36", and 1000 watt for 36"+.
A single 400 watt metal halide can produce 4000mE of light. Double Ended HQI bulbs with higher output ballasts can produce 30% more output than mogul (screw in) bulbs. Metal halide bulbs produce significant heat and proper ventilation is a must. The bulbs require replacing approx, every 12-14 months. Other Considerations..Color Temperature:We recommend that the light source you use be within the range of 10,000-20,000 Kelvin. 10,000K being on the white end of the scale and 20,000K giving the highest appearance of actinic blue. The presence of both spectrums is important. A mixture of 10,000K(white) and an actinic blue (14,000-20,000K) seems to give the appearance of choice for many reefers.Reflectors:The use of reflectors help your lighting achieve its highest potential, a great bulb with a poor reflector isn't going to net great results!Ballasts: There are 2 types of ballasts available: Magnetic and Electronic, magnetic are less expensive and most commonly used. Electronic ballasts have a higher efficiency rating so less power is consumed and usually longer bulb life results.
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