Many aquarium plants require more intense light to thrive than typical aquariums provide. The common guideline is to provide at least 4 to 5 watts of lights per gallon of water for a planted freshwater aquarium. Several types of lights are available, and each has pros and cons.
The first choice in aquarium lights is normal output or NO fluorescents. These are standard aquarium lights, and cost less than other types of aquarium lighting, but may require multiple lighting fixtures to meet the needed amount of light for a planted freshwater aquarium. Typically these bulbs work best for fish-only tanks, and planted tanks that only feature low-light plants.
More advanced types of fluorescent lighting are also available. These are high output or very high output (HO/VHO) lighting, which includes such innovations as powered compact lighting. These are twisted fluorescent tubes, similar to the compact fluorescents found in many modern buildings. T5 lights are another type of VHO fluorescent lights, and provide very high output.
Metal halide lights are another type of powerful lighting. Their strong, point-source lighting makes them popular with saltwater hobbyists for coral tanks. They may be overkill for most planted aquariums, and cost more than other types of light. However, their powerful light can easily shine through to the bottom of deeper aquariums, so they may work well for very deep planted freshwater tanks. Also, since they generate light from a single point, their light ripples across the bottom like real sunlight. Many aquarium hobbyists like the way these lights look.
LEDs are the latest innovation in aquarium lighting. They work somewhat differently from bulbs and fluorescent tubes, producing less heat than other types of lighting and using less electricity. For example, an LED array with the same light output as a metal halide light uses 20 percent less electricity. The biggest drawback to LEDs right now is their cost. However, this is dropping as more people adopt the technology. They work well on planted aquariums, though it can be trickier to calculate the necessary watts per gallon with these lights. Fortunately, most commercially available LED arrays come with guidelines for how much illumination they provide.
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