Too light or not too light…that is the question - or at least the question on every reefkeepers lips. In the hobby today, lighting is one of the most controversial subjects. Even the experts disagree. As new technology advances come to market in the lighting area, we are all struggling to keep up with the new bulbs, ballasts, dimmers, etc. I have been in the hobby for 15 years and have tried quite a few different bulbs and lighting techniques (not to mention spent a lot of dollars.) In this article I am going to share some of the things that I have picked up over the years.

When you set up a reef tank or you have an existing one and want to change lighting, there are a few things that you may want to consider. If this is a new tank, you need to consider what type of tank you want it to be. For instance, soft corals will do just as well under 40 watt fluorescent bulbs as under metal halide lights. "SPS" (Small Polyp stoney) corals on the other hand demand stronger lighting.

Whether you decide to go with fluorescents, metal halide or power compact fluorescents, first of all make sure you check how many amps your ballast will run. Four hundred watt ballasts will run at 4 amps, so when you combine two or three bulbs, with all your pumps and gadgets, you may blow your circuit breakers.

More times than I can count, I've seen reefkeepers install their tanks, get them up and running, and turn on the lights and "poof" - the breaker blows. Often, to make matters worse, the outlet is behind the tank. So, make sure that you add up the amperage before you install anything. When you are ready to purchase your ballasts, always ask your dealer to make sure they are UL listed. UL stands for Underwriters Laboratory and parts that receive this listing must go through extensive testing before they receive this label. If it does not say "UL Listed" on the unit, it may not be completely safe. 

Also, it is a good idea to bridge your ballasts across a couple of concrete block (cinder block) or a couple of bricks. This is a good idea for two reasons. First, it will raise the ballasts off of the ground or the bottom of the cabinet. By bridging the ballast on two bricks, you will help airflow underneath it and help to keep it cool. The second reason is that ballasts run very hot, depending on the wattage you use, and it is not a good idea to put the ballasts on flammable material, like carpet or wood or anything that could cause a fire.

Bulbs: There are many types of bulbs: fluorescent, VHO (Very High Output) Fluorescent, Power Compact Fluorescent and the many varieties of metal halide bulbs with Kelvin ratings of 5500, 6500, 10,000, 14,000, 20,000. 

The color temperature of the bulb is referenced in degrees Kelvin (K), with the higher the color temperature, the whiter the bulb. That is because the violet blue and green parts of the color spectrum prevail. If the color temperature of the bulb is lower, the warmer the appearance of the light, with the orange and red hues of the spectrum dominating. One of the main topics of debate is which Kelvin rating is best for which corals so as to keep their natural colors.

Most of the corals that are imported today are from waters ranging from 10-20meters deep (33-66 feet). If  you have ever gone snorkeling or scuba diving, or just watched an under water video, you know that at those depths, the color of the water is blue. The orange and red spectrum is drastically reduced; thus there are more violet blues and greens at those depths. Unfortunately, the higher the Kelvin rating of the bulb, the lower the intensity. So, therefore you will need a higher wattage bulb if you decide to use a 20,000K-rated bulb. 

Every bulb runs differently, even if you compare ones made by the same manufacturer. Metal halides in particular are prone to large variations in lux readings, sometimes 1000 more or less difference.  Metal halides bulbs run very hot, so unless you have a chiller or some other way to keep the water cool I do not recommend using these bulbs. Also, metal halides are meant to run at room temperature, so if you have fans in your canopy, especially strong ones (90 cfm or cubic feet per minute or higher), do not aim them directly at the bulbs. I have done this and found out that the bulb will run dimmer because it is being cooled too much. Metal halide bulbs should be changed at least once a year. I personally change them every six months to drastically reduce the shock of new bulbs on the animals. When you change bulbs, you should cut your photo period to 3 hours and build up to your maximum time over a period of 1 1/2 - 2 weeks. If you do not do this, you will soon find your corals turning white (bleaching).

Fluorescence: Fluorescent bulbs come in different forms for the aquarium hobby.  The standard bulbs come in 15, 20 and 40 watts while VHO bulbs come in 75, 95, 110, 140 and 165 watts. The compact fluorescent bulbs are also a high wattage fluorescent. They come in 55 and 96 watt. All of this type or family of bulbs certainly run more efficiently than metal halide bulbs (per watt to amp). They will also run cooler than halides. The only drawback to these bulbs is that they are not as intense as metal halides and they need to be changed every 6 months (except the compact fluorescence, which some manufacturers claim will last for 3 years.) Unfortunately, I have had some of these bulbs and so far they have lasted about one year to 1 1/2 years. I am in the process of trying new compacts, but they have only been on the market for about a year, so, we'll see.

Reflectors: It is very important that you use a reflector so you don't waste all that money you spent on bulbs and ballasts, because if you don't reflect the light, you will have lost about 1/3 - 1/2 of the bulb's capacity. There are quite a few reflectors on the market, sold by themselves or in lighting units. I had asked a friend of mine who is an optical engineer which surface would reflect best. She said that a mirror is the best reflector you can use. Unfortunately, because I was using 400-watt bulbs, I could not use a lightweight plastic mirror because it would have melted. Glass was just too heavy to install in the canopy, considering the size glass mirror I would have needed. The next best thing was a polished aluminum reflector. Today, reflectors come in white, which disperses the light but also softens it, so you actually lose some of the light. There are the hammered reflectors that have an inside surface like a bunch of dimples. The points of light bounce off of the dimples and back into the water. The end result is an even coverage, but a loss of some of the intensity.

Whichever lighting system you decide to go with, remember to light the tank according to the type of animals you will be keeping. Why spend the money on a metal halide system if you are going to keep mushrooms. I hope this will column will help you with some of your choices, or at least help a few of you before you whip our your checkbook.