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Reef Aquarium Lighting: The basic rules.

© Winston Vaughan Schoenfeld

In all aquariums there are sources of nourishment and growth. Freshwater aquariums usually house fish, and thus a major portion of the nourishment of the living organisms in the aquarium comes from the food that you put in the aquarium. For reef aquariums, this is not necessarily the case. The food you put in the aquarium does provide energy that the species in it need, but lighting plays a much larger role than in fresh and saltwater aquariums. The invertebrates and reef growth thrive on the correct lighting. Slight changes in the lighting can have large effects on the health of your reef structure. So, what is ideal, and what basic rules do you need to obey? Below I will outline some of the basis guidelines.

How much light?
You want between 3 and 5 watts of light per gallon of aquarium. For example, if you have a 50 gallon aquarium, you want between 150 and 250 watts of light. Too much light will promote algae growth, and too little light will deteriorate the health of your reef life.

What type of light is best?
The first thing I should say here is that you shouldn't keep the aquarium in direct sunlight. It will cause algae growth to occur rather rapidly. Basically there are two particular colors of light that are very important to a reef aquarium: blue and greenish-yellow. Most aquarium bulbs leave out the red portion of the spectrum. This is due to the fact that it tends to promote micro-algae growth which is not good for the reef aquarium. This is why normal "house" bulbs should not be used. They do not omit the portion of the visible spectrum which is undesired. You must buy aquarium bulbs. Generally a mixture of full spectrum and actinic blue bulbs is desired. These bulbs are similar to the basic fluorescent bulbs found in many households. For those with larger aquariums, you may find that you need to use metal halide lighting to produce the intensity of light needed, but be aware that these types of bulbs generate a great deal of heat.

How long should the lights be on? The general rule is 8 to 9 hours. Leaving lighting on for more than 8 to 9 hours will have some ill effects on the aquarium. In short it will promote algae growth. The easiest way to keep the number of hours of lighting constant is to use a timer. These are not very expensive, and are a great investment.

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