(PART-1)
Lighting the Reef Tank: A Primer for Beginners
The subject of reef tank lighting is one of the most controversial subjects in the reef keeping hobby. Lighting is often a hotly debated topic because there are people who have had success or failure with each different type of lighting system used in the hobby. The most important consideration for reef tank lighting lies in choosing a lighting system based on the requirements of the animals that we wish to keep. While many reef keepers are concerned with the appearance of their reef tank, their main concern should be the health of the light requiring animals that they are attempting to keep. As many corals and other animals have symbiotic zooxanthellae that utilize light energy, the lighting system must meet those animals' needs, both in terms of intensity and color spectrum. The definitions of intensity and color spectrum are beyond the scope of this article, but I will include some useful references at the end of this article.
The commonly used phrase, "watts per gallon," is a way of expressing the lighting necessary for a tank by the ratio of the power used to illuminate the tank divided by the tank size in gallons. Many hobbyists suggest that an adequate amount of light would vary between four watts and six watts per gallon for low light coral and as much as ten watts per gallon (or more) for light loving coral. While such a rule of thumb may initially sound like a good idea, it should only be used as a rough guideline and not as a strict rule. Obviously, such a loose rule is misleading, and aquarists need to consider more than just "watts per gallon." Specifically, they must take into account the height and overall size of the tank. A tank that is 36 inches tall will require more light intensity to reach corals on the bottom than it would with a tank that is only 24 inches tall. For example, all 120 gallon tanks would require 480 to 720 watts of light based on the "watts per gallon" guideline, regardless of their depth, so a 120 gallon tank that is two feet tall, by four feet wide, and two feet deep would seem to need the same lighting as a 120 gallon tank that is three feet tall, by two feet deep, and three feet wide. The second tank, however, is a foot taller. Since the intensity of light decreases as the square of the distance from the light increases, the amount of light needed is much greater if the same corals are to be kept on the bottom of each tank.
(cont. part-2)
Lighting the Reef Tank: A Primer for Beginners
The subject of reef tank lighting is one of the most controversial subjects in the reef keeping hobby. Lighting is often a hotly debated topic because there are people who have had success or failure with each different type of lighting system used in the hobby. The most important consideration for reef tank lighting lies in choosing a lighting system based on the requirements of the animals that we wish to keep. While many reef keepers are concerned with the appearance of their reef tank, their main concern should be the health of the light requiring animals that they are attempting to keep. As many corals and other animals have symbiotic zooxanthellae that utilize light energy, the lighting system must meet those animals' needs, both in terms of intensity and color spectrum. The definitions of intensity and color spectrum are beyond the scope of this article, but I will include some useful references at the end of this article.
The commonly used phrase, "watts per gallon," is a way of expressing the lighting necessary for a tank by the ratio of the power used to illuminate the tank divided by the tank size in gallons. Many hobbyists suggest that an adequate amount of light would vary between four watts and six watts per gallon for low light coral and as much as ten watts per gallon (or more) for light loving coral. While such a rule of thumb may initially sound like a good idea, it should only be used as a rough guideline and not as a strict rule. Obviously, such a loose rule is misleading, and aquarists need to consider more than just "watts per gallon." Specifically, they must take into account the height and overall size of the tank. A tank that is 36 inches tall will require more light intensity to reach corals on the bottom than it would with a tank that is only 24 inches tall. For example, all 120 gallon tanks would require 480 to 720 watts of light based on the "watts per gallon" guideline, regardless of their depth, so a 120 gallon tank that is two feet tall, by four feet wide, and two feet deep would seem to need the same lighting as a 120 gallon tank that is three feet tall, by two feet deep, and three feet wide. The second tank, however, is a foot taller. Since the intensity of light decreases as the square of the distance from the light increases, the amount of light needed is much greater if the same corals are to be kept on the bottom of each tank.
(cont. part-2)