Perhaps there is no other topic in Reef Tank keeping that is more hotly debated than the issue of Reef Tank Lighting. Ask 20 different Reefers what’s the best lighting and I will bet the bank you will get no less than 21 different answers! In the following paragraphs I will try my best to provide an unbiased over view of each suitable form of lighting, its advantages and disadvantages. This will be very general in nature and I will cover each in great detail in future articles that are forth coming.

First before we begin, we will be using a number of terms and abbreviations. As such I will outline and define each in layman’s terms as best possible.

Kelvin; A unit of measurement used to describe the temperature or “color” of the light waves produced by a light bulb.
PAR; A abbreviated term commonly used in Reef Keeping to describe and measure a light bulbs intensity or “Brightness”.
NO; Is a term used to describe “Normal Output” fluorescent light tubes.
HO; Is a term used to describe a series of bulbs that are “High Output” fluorescent light tubes. These typically provide 2 times the wattage per a given length of NO tubes.
VHO; Is a term used to describe a series of bulbs that are “Very High Output” fluorescent light tubes. These typically provide 3 times the wattage per a given length of NO tubes.
PC; Is an abbreviation for Power Compacts. These are unique fluorescent tubes that are relatively new on the market and have only been available for few years.
Halides; Are Metal Halide lights. These are similar to incandescent bulbs and come in single ended bulbs (SE) or double ended bulbs (DE). Due to differences in bulb design these bulbs are run off of Ballast that have been specifically designed for a specific bulb and in most cases ballast or bulbs cannot be interchanged! Do not confuse these with High Pressure Sodium (HPS) lighting or Mercury Vapor (MV) lighting, as there are some huge differences.

Now for some more basics before we get too far along. In the Saltwater community for years Reefers have used a formula of “Watts per a Gallon”. In the early days of Reef Keeping this formula had some validity, but in today’s age of technology, and given our more thorough understanding of lighting requirements, this formula is all but useless. The reason for this as I will later point out in later paragraphs fails to take too many other variables into account, such as tank depth being the more important specific. It doesn’t consider PAR or Kelvin ratings of light bulbs either and in a Reef Tank this can mean the difference of success or failure!!! Natural sunlight has a Kelvin rating in the neighborhood of about 5500 Kelvins. Typically you will want to use as a minimum a bulb which has a Kelvin Rating of at least 6500K’s. Most Reefers will use bulbs typically 10,000K’s to 20,000K’s The Higher the Kelvin Rating the more blue light that is in the light spectrum from the bulb in question. This is of critical importance to reefers for two reasons. One the lower the Kelvin Rating of the bulb the more Red light waves the bulb produces. This gives a yellowish look to the tank and this temperature favors algae growth more so than the higher Kelvin bulbs do. With the intensely light reef tank this can cause algae blooms that cam turn even the best tank into Pea Soup in no time. The higher Kelvin rating of bulbs on the other hand will encourage coral growth and coloration more so than algae growth. Additionally corals require some light in the 420 nm range to thrive. Higher temp bulbs better assimilate this wavelength in light waves. With that tid bit outta the way…lets get down to business.

NO lights. These are your typical fluorescent lights like the ones found in office spaces and such, and in aquariums usually come in sizes of T-12 and T-8. Each of these two sizes will come in various lengths and wattages. For example…a T-12 NO that’s 48 inches long will typically produce 40 watts of light. The same length T-8 bulb will produce just 36 watts of light. This type of lighting has minimal uses in a saltwater tank. It is most commonly used as lighting in Fish Only or Fish Only With Live Rock. It is also used for Actinic lighting supplementation to other forms of more intense lights. It does however provide for uses in a Reef Tank in limited circumstances for “Soft Corals” such as Mushrooms and various Colonial Polyps if the tank is fairly shallow. The advantages to using this bulb is they are widely available and reasonably cheap as are the fixtures that use them. The downside is that like all fluorescent bulbs must be replaced after 6 months of use, as their color spectrum will seriously begin to shift making them unserviceable. Additionally due to the huge amounts of light required by most reef tanks it’s almost impossible to cram enough of these fixture under a tank canopy to provide sufficient light. Another downside that affects all fluorescent lights is their ability to penetrate water. After about 16 inches of water, fluorescent lights begin to seriously drop off in the level of PAR they can provide

HO lights. These are relatively new outside of Europe. They produce significantly more light than NO bulbs do. A 48-inch T-5 bulb will typically produce 54 watts of light. However due to their small ½ inch diameter, one can cram a whole lot of these fixtures under the canopy making them quiet suitable for any soft coral and most LPS corals and some SPS corals and light demanding clams. While I have seen these lights in operation and can attest to their brightness they still share many of the shortcomings of NO bulbs, just not to the same extent. Bulb Life is rumored to be about 9-12 months and the PAR on them is a bit more intense than NO’s as well.

PC lights. These bulbs are very compact size wise and come in several different K ratings. They are fairly intense and as such allow a Reefer to pack a lot of wattage into a small confined space. They can be had in wattages as low as 9 watts all the way to 96 watts. While these lights are very efficient lights they have one very serious draw back! When it comes to providing actinic light these fall a bit short being able to only produce 450 nm at best. In my experience these lights are best suited to small Nano-Reefs and tanks under 40 gallons as their compact size make providing adequate light in tanks this small most efficient. But in actual use while they are adequate I have found that VHO’s out perform them in color rendition and in suitability in regards to coral health, color and growth. But none the less one can be quiet successful with these lights none the less and there are a lot of great looking tanks out there to back that up. These bulbs require annual replacement as the color shifts significantly after that amount of use.

VHO; If restricted to fluorescent lights and you have a tank 36 plus inches long, then VHO is tough to beat. It’s been on the market longer than any other form of fluorescent lighting with the exception of NO’s. As such the R & D on VHO is about as advanced as any. It too is T-12 in size but a 48-inch bulb will knock out a whopping 110 watts of light. It has excellent color rendition and provides exceptional PAR. It’s available in lengths from 24 inches to 72 inches with wattages of 75 to 160 watts. Actinic bulbs in this format will produce a true actinic color in the 420 nm range. The only downside is the bulbs as with most fluorescent tubes will be required to be replaced at 6 months or their abouts depending upon what type of ballast is being used. This is also probably the most cost efficient form of fluorescent lighting as well from a cost stand point VS wattage. This light possesses enough PAR that it is excellent for Soft corals and LPS corals and does a decent job with all but the most demanding SPS corals and Clams. It’s personally my lighting of choice except when halides aren’t being used. Even then, it’s awesome for backing up halides lights when actinic lighting is needed for supplementation.

Halides; Now this is truly the penical in Reef Tank lighting for all but the most light sensitive Soft corals. Unlike other forms of lighting the PAR and Kelvin temps of Halide bulbs make this a superior for of lighting for Reef Tanks in more cases than not. The down sides are that they are a bit pricey, especially the DE fixtures. The other aspect is the cost of bulbs, but when one considers that they are good for 12-16 months depending on the ballast used, their cost is quiet comparable. Contrary to popular belief…halides aren’t really any hotter than other forms of lighting of equivalent wattage. They are how ever more concentrated in their heat out put and therefore can cause hot spots with in the tank and if placed to close to the water cause over heating of the tank. When bulbs are elevated 8-10 inches above the tanks water and the canopy properly ventilated they will add little additional heat to the water temp. Under halides most corals will show accelerated growth. Generally speaking those desiring rapid growth will use 6500K Isaki or Ushio brand bulbs. Those desiring optimal color of corals as opposed to growth may want to opt for the XM 20000K or AB 20000K. When using 14000K bulbs or “cooler” bulbs supplemental actinic lighting may not be required. However remember as the Kelvin rating gets higher numerically the PAR in these bulbs will drop off significantly. As such most Reefers will use a mix of different color temps or move up one size in wattage to offset the loss in PAR with these lights. Halides come in 70 to 1000 watts with 150-400 being most common.

Hopefully you were able to garner a little bit more knowledge about Reef Tank lighting than you previously had. I will be providing further information in up coming articles as I spot light each one individually. In the meantime Good Luck and Happy Reefing!