Lighting is one of the most important aspects of a professional looking aquarium. While lighting in a fish only tank is only used to physically see the fish, reef and planted tanks use lights to actually keep aquatic life alive. Light can also encourage algae growth, some nuisance, and some beneficial. It is always recommended to use a timer with your lights to ensure consistent lighting intervals. If your tank is over 24 inches deep you should use a metal halide type light and fixture. The deeper the tank you have the more lighting power you will need. Since each bulb can only penetrate so far into the water, you cannot simply add more lights if your tank is deep, you will need more powerful individual bulbs. A 400 watt Metal Halide lamp can penetrate deeper than 20 individual 54 watt fluorescent lamps, even though the fluorescents have way more total wattage. A good rule of thumb is to have about 2-3 watts for freshwater planted aquariums and 8-10 watts per gallon of water for reef tanks and high light requirement corals. Additionally, you may want to consider LED lighting as well - fixtures like the Orphek are changing aquarium lighting dramatically.
Color Types & Aquatic Life Lighting Basics
Kelvin Rating is a measurement in numerical form to show what type of ‘color temperature’ the bulb will produce. The color temperature is determined by comparing the color of the light emitted (not luminance or wattage, or intensity, just the color) to what is called a black body radiator. A black body radiator is an idealized object that absorbs all light and reflects no light, so it will appear black when cold. However, when this body is heated it starts to turn colors. The colors this body turns is compared to its temperature in degrees Kelvin. Generally a Kelvin rating of 1500 will produce a red color, as the Kelvin color temp increases it will turn green to yellow (around 3,000K – 4,000K) and then into a yellow sun color around 5,700 – 6,000K. Anything after 10,000K (Whitish blue color) will start to turn blue.
Nanometers(nm) are also used to measure the wavelength of a light. Refer to the magnetic spectrum and more specifically the visible light section between 700 and 400nm. Nanometers are the actual measurement of the wavelength produced by the lamp from peak to peak, or valley to valley. Generally wavelengths cannot be converted to color temperature (K) and vice versa. 700nm starts the red colors and continues to green around 600nm. 500nm is about the middle of all Green colored light and 400nm will produce a blue to violet colored light.
For individual description of different lights click the category above that pertains to your type of bulb.
