Often, while researching coral, the beginner aquarist will see general light requirements for that particular species. They will generally see one of three words: Low, Moderate, and High.
Now, while this seems straightforward, it is often difficult to interpret what your lighting qualifies as. It also affects the placement of coral within your tank, so it is important to determine what your lighting qualifies as. Lighting is very difficult to measure in our hobby, and "high" or "low" lighting is usually 'guesstimated' by fixture wattage, type of lighting, and reflector(s) used. Because most aquarists do not have access to a PAR meter, this is usually the most accurate form of light interpretation that can be hoped for.
T5HO is generally considered moderate to high lighting, again dependant on the height of the tank and the wattage of the fixture, as well as the size and shape of the reflectors. If using a T5 fixture, the reflectors used are very important. SLR, or Single Light Reflectors, vastly improve the amount of light going in to the tank. T5 also depends on how many bulbs are in the fixture. These can be used to keep all types of “Softies,” all varieties of LPS and SPS, again dependending on the fixture.
Metal Halides, until LEDs eventually replace them (and all other forms of aquarium lighting! - Editor), are still one of the top choices for lighting SPS, especially in deeper aquariums. While they run the risk of photoinhibiting lower light coral, such as LPS, it can also maintain all varieties of SPS, and do so in taller tanks. It has become a common practice to use high wattage metal halide fixtures over smaller aquariums, an absurd practice that usually results in the photoinhibition of the hobbyists' corals.
One thing to remember when gauging your set up is that watts per gallon is a rule that is completely inaccurate, as light fixtures don't "produce watts of light", they simply use electrical energy (measured in watts) to produce light energy. Instead, the aquarist should focus on achieving the most photosynthetically active radiation (PAR) per given wattage and/or depth, taking into account the lighting needs for the types of coral they want to keep. For more detailed lighting information, check out our post on lighting photosynthetic marine invertebrates.
Power Compacts are generally thought of as lower light, all though if you have a high wattage on a shallow tank, it could be interpreted as moderate light. These fixtures are generally used by beginners, and can safely maintain most “Softies” and many varieties of Large Polyp Stony coral.
T5HO is generally considered moderate to high lighting, again dependant on the height of the tank and the wattage of the fixture, as well as the size and shape of the reflectors. If using a T5 fixture, the reflectors used are very important. SLR, or Single Light Reflectors, vastly improve the amount of light going in to the tank. T5 also depends on how many bulbs are in the fixture. These can be used to keep all types of “Softies,” all varieties of LPS and SPS, again dependending on the fixture.
Metal Halides, until LEDs eventually replace them (and all other forms of aquarium lighting! - Editor), are still one of the top choices for lighting SPS, especially in deeper aquariums. While they run the risk of photoinhibiting lower light coral, such as LPS, it can also maintain all varieties of SPS, and do so in taller tanks. It has become a common practice to use high wattage metal halide fixtures over smaller aquariums, an absurd practice that usually results in the photoinhibition of the hobbyists' corals.
One thing to remember when gauging your set up is that watts per gallon is a rule that is completely inaccurate, as light fixtures don't "produce watts of light", they simply use electrical energy (measured in watts) to produce light energy. Instead, the aquarist should focus on achieving the most photosynthetically active radiation (PAR) per given wattage and/or depth, taking into account the lighting needs for the types of coral they want to keep. For more detailed lighting information, check out our post on lighting photosynthetic marine invertebrates.
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